Justine Greening MP is asking John Bercow, who was elected as Speaker last month, to ensure that MPs receive accurate and complete answers. She told him: “The need for transparency and accountability of ministers and Parliament has never been higher.”

In her letter, Greening, MP for Putney and shadow minister for London, listed five examples of written parliamentary answers where ministers either failed to answer her questions or provided answers that have subsequently been shown to be untrue.

Four of the five cases concern plans to expand Heathrow airport. The most recent involves a letter that BAA chief executive Colin Matthews sent Hoon last November. At the time, BAA issued a press release stating that it would ask the government to appoint an independent assessor to ensure that an expanded airport would only increase flights if it operated within environmental limits — a policy that was adopted by Hoon in January.

But the letter itself was not published. I made a freedom of information (FOI) request for it in March. The Department for Transport (DfT) refused to release it, citing an obscure section of the Environmental Information Regulations (EIR) and claiming that the letter’s contents were set out in BAA’s press release. Greening then tabled a parliamentary question asking for the letter to be placed in the House of Commons library. The government refused, also on the grounds that the press release contained “the substance of the letter”.

When Greening tabled a further question, asking for an explanation of this refusal, aviation minister Paul Clark, claimed that the contents of the letter were covered “in full” in BAA’s press release.

But I have obtained a copy of the letter from BAA [click here to read]. It contains a number of elements that were not in the press release, including an admission from Matthews that “for many people the environmental consequences of expanding Heathrow remain a major concern, and some have serious questions around how the noise and air quality limits will be met.”

The letter also included technical information that was not disclosed by the press release. It linked the role of the independent assessor for the third runway plans with an earlier proposal that a reformed slot allocation system would be the method used to limit flights. This would make the assessor’s findings independently enforceable. It also revealed that BAA had made this earlier proposal in February last year, in its response to the official consultation. That response — and therefore the earlier proposal — is no longer in the public domain, and the press release made no reference to the proposal.

The DfT’s response to my request raises questions about the tactics that the department is prepared to employ to block the release of information, in stark contrast to Gordon Brown’s recent promises of more transparency.

Both the FOI Act and the Environmental Information Regulations include exemptions that allow public authorities to refuse to disclose information that is available elsewhere. In its response to my request for a review of the DfT’s decision, a senior official asserted that because the letter and the press release covered the proposal for an independent assessor in the same terms, “the information contained within the two documents is the same”. She also offered reassurance that all the “relevant” information was in the public domain.

The DfT’s approach in this case concerns Maurice Frankel, director of the Campaign for Freedom of Information. He told me: “It was unnecessary and pedantic, and not releasing the letter was bound to create suspicion. They shouldn’t be assessing what you need to know. The regulation cited does not allow any information to be withheld, however insignificant or irrelevant it may be or be judged to be.”

A DfT spokesperson said: “This decision, made under EIR rules, was that the information requested was publicly available and easily accessible already, as it was contained in a BAA press notice issued in November 2008. The decision was internally reviewed and upheld.”

Another case in which Greening says a minister gave a misleading answer to a question also involves BAA’s lobbying over the new runway.

Ian Pearson, then a minister at the Department for Business, had appeared to claim that ministers had not met the aviation industry to discuss Heathrow expansion. But a letter from Peter Mandelson to Matthews revealed that business minister Baroness Vadera had met the BAA chief executive to discuss new runway capacity. The Department for Business claimed that Pearson had not answered inaccurately because no specific meetings about Heathrow had taken place.

But Greening disputes this. She told Bercow: “MPs should not need a degree in law to be able to word parliamentary questions to get adequate answers or to be able to ascertain the exact nature of a Ministerial response.

“The alternative of using the FOI route is cumbersome and deliberately dragged out by departments, but that is increasingly the route I take because I find that too often I cannot rely on the adequacy or accuracy of ministerial answers to my parliamentary questions.”

Greening famously obtained proof that BAA helped the DfT to ‘reverse-engineer’ its forecasts to show that a new runway would meet ministers’ ‘strict environmental tests’. This evidence came from a request for disclosure of communications between the two organisations. But the DfT has refused two almost identical requests from Greening covering later periods. The Information Commissioner, Richard Thomas, is expected to rule shortly on her complaints.

Many of the papers the DfT is withholding cover the period immediately before it launched its consultation document on Heathrow expansion in November 2007. The department has disclosed that they include around 30 exchanges, which ‘without exception… relate to the preparation of the final supporting technical reports (all since published) or to BAA technical input to the main consultation document’. The two reasons it has given for withholding these exchanges have already been rejected by Thomas.

The main reason cited by the DfT, using provisions in the environmental information regulations rather than the very similar FOI Act, are that they are ‘unfinished’. Thomas has already ruled in an earlier case — albeit one that the DfT is appealing — that this provision simply does not apply to early versions of papers that have since been published.

The DfT’s reason for concluding that the balance of public interest requires suppression of the documents is even more clearly against both the spirit of FOI laws and the letter of Thomas’s published guidance. Although the department has admitted that the papers ‘could give insight into how the final documents were developed’, it has claimed that this would lead to a ‘distorted view of how the final documents developed’ and to ‘ill-informed’ speculation.

If not a direct admission that the papers are damaging, this is as close as you will ever see in a refusal notice to such an admission. This type of negative approach to information requests has been specifically ruled out in guidance published by Thomas, who says that the answer to ‘ill-informed’ speculation is more, not less, information.

But the DfT seems unable to conjure up any reason to refuse Greenpeace’s request. The environmental campaign group previously obtained the department’s risk register documents for the airport expansion project, which showed how officials said one thing in private and something very different in public, particularly as ministers prepared to launch the consultation. Last October it put in a new request for later versions of the same documents.

Four months on, the DfT has yet to provide a substantive response, in spite of a statutory requirement to do so within 20 working days.

Ben Stewart, Greenpeace’s head of press, who made the request, says the official handling it initially told him that it would be straightforward, requiring only an assessment of which parts of the documents needed to be ‘redacted’, meaning censored.

But then things became complicated. The case was linked with one from another requester, later said to be Greening, in which an internal review was said to be ongoing. Although there is no provision in the FOI Act for delay on these grounds, delay is what the DfT has done ever since.

Stewart says: ‘I thought it would be straightforward to ask for and get the latest in a series of documents that had already been released. As it is, over the past few months, I have had some of the most bizarre conversations of my life with DfT officials, who seem incapable of abiding by a single aspect of the FOI regulations. First they simply ignored my request, then they promised me the documents by the end of the week, every week.

‘They then dispensed with serial misrepresentation and went instead for the silent treatment, replying to every question with the phrase ‘I will only discuss this with you in writing’, even when I asked them how they were. So I wrote, and they didn’t reply. I phoned to ask if there was an information rights team at the DfT — as there is at most Whitehall departments — but this question was addressed as if it was a matter of national security. They simply couldn’t talk about the existence or otherwise of such a team.’

The DfT has declined to comment on the grounds that the case is still under consideration. But the Information Commissioner’s office has now written to the department twice about the case, including a letter in December from the assistant commissioner, Gerard Tracey.

Last week Stewart received a call from the information rights department at the DfT — which does indeed exist — to apologise for the treatment he has received. But, unsurprisingly for a spin doctor, he is quick to point to an obvious conclusion: ‘I’m wondering, if Hoon’s case for a third runway is so strong, what is he hiding?’