The former editor-in-chief of the Telegraph told the Leveson Inquiry he felt it was his duty, not a choice, to publish the paper’s revelations about MPs’ expenses in 2009.

Will Lewis said it was his “ethical obligation to bring this profound wrongdoing at heart of House of Commons into public domain.”

Lewis said it was a topic that was “laced with risk all round”. Having worked for the Sunday Times when it printed the fake Hitler diaries in 1983, Lewis also said he was concerned the expenses story was a hoax.

Lewis described the role of an editor as risk mitigation. “At the end of the day you have to ask yourself, ‘does it feel right?'” he said, adding that mistakes he had made in his career came about because he had not followed his instincts.

He urged for a greater focus on a more transparent newsroom culture, noting that “sunlight is a fantastic disinfectant.”

The paper’s current editor, Tony Gallagher, also testified today, arguing that the best outcome of the Inquiry would be an arbitration system for resolving legal disputes and complaints. “The chilling effect of libel on small media organisations has to be seen to be believed,” he said.

Earlier in the day Lord Justice Leveson also spoke in favour of a low-cost libel mediation system. He cautioned against government involvement, telling Telegraph Media Group CEO chief executive Murdoch MacLennan, “I would be surprised if government regulation ever even entered my mind.

The Inquiry continues tomorrow, with evidence from Associated Newspapers.

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