An out-of-government Malcolm Tucker and the hapless Nicola Murray MP are set to return to BBC2 for a fourth series – the first since 2009 – with the corporation confirming it will be a case of art imitating life to reflect real-life changes in Westminster in the interim.

"This series takes The Thick of It into exciting and uncharted territory: a new coalition government, and Malcolm and Nicola fretting in the wings," said Iannucci, who dropped his second hint in as many months that the characters will have to contend with a public inquiry.

"For the first time too a storyline takes us all the way through the series right to the bitter, bitter end, with government and opposition convulsed in an incident that questions every political convention imaginable, but in a funny way," the writer added.

Last month he told an audience of journalists at a private screening of Sky Atlantic's Veep, his new US vice-presidential comedy, that the Leveson inquiry into press standards provided prime material for lampooning.

"It is interesting watching them all swear on oath and then saying what they say," he said at the time. "Tony Blair was giving – for want of a better word – his evidence."

The BBC2 controller, Janice Hadlow, said that the new seven-part series – which will air in September – was an "essential" part of the channel's comedy offering this year. Iannucci directs the penultimate 30-minute episode in the series.

Rebecca Front and Peter Capaldi will return, as will Roger Allam as Peter Mannion MP, the new secretary of state for the department of social affairs and citizenship.

Vincent Franklin plays No 10 director of communications Stewart Pearson, while Geoffrey Streatfield will play new coalition partner Fergus Williams MP, the junior minister at Dosac.

"I'm excited to see The Thick of It return to our screens," said the BBC head of comedy, Mark Freeland. "With an outstanding cast and team, it is still at the bleeding edge of British politics."

The new series was written by Tony Roche, Simon Blackwell, Ian Martin, Will Smith, Roger Drew and Sean Gray.

Additional material was written by David Quantick, Dan Gaster, Georgia Pritchett and Rob Colley.

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