Gordon Brown will give evidence to the Iraq inquiry next Friday, it was announced today.

He is scheduled to take questions for around four and a half hours about his involvement in Iraq policy both as chancellor and as prime minister.

Sir John Chilcot and his team originally said that they did not want to call Brown before the general election because they did not want his evidence to be exploited for party political purposes.

But Chilcot changed his mind after the Liberal Democrat leader, Nick Clegg, suggested that Brown had something to hide. Chilcot decided that it would be unfair to Brown not to let him give evidence before polling day.

The inquiry has heard evidence that the Treasury did not give the Ministry of Defence all the resources it wanted and Brown is likely to be asked about this in detail.

But he may also be asked whether he was in favour of the decision to go to war. Although Brown has defended the war, he said little about it in public at the time, and there were claims that he privately believed that the invasion was a mistake.

In an interview at the weekend Brown insisted that he did support Tony Blair's decision to use military force.

"For me, it's always been about a country that refused to cooperate with the international community over many, many years, when it was in breach of its international obligations," Brown told the Independent on Sunday.

"In Britain, it's a cabinet decision. You accept the collective responsibility in a cabinet, and I would expect every member of a cabinet I was in to accept their collective responsibility. When a decision's made you've got to stand up and defend it."

Two other cabinet ministers who were also originally going to be questioned by the inquiry after the election will also appear in early March.

Douglas Alexander, the international development secretary, will appear next week after Brown, on Friday afternoon. David Miliband, the foreign secretary, will give evidence the following Monday.