Jeremy Corbyn has apologised on behalf of the Labour Party for the decision to go to war in Iraq.

The Labour leader issued an unprecedented apology to the people of Iraq, bereaved British families and the public in this country.

Hours after the publication of the Chilcot report today, Corbyn told an audience in London: “I now apologise sincerely on behalf of my party for the disastrous decision to go to war in Iraq in March 2003.”

The decision to issue an unreserved expression of regret, which had been widely expected after 13 years spent denouncing Tony Blair’s decision to invade, goes further than that of any previous Labour leader.

Corbyn today said he wanted to apologise to Iraq, where the death toll has run into hundreds of thousands of people, to the families of British service men and women who had been killed or returned home with serious injuries, and to the “millions of British citizens” whose faith in democracy had been “undermined”.

“That apology is owed first of all to the people of Iraq. Hundreds of thousands of lives have been lost and the country is still living with the devastating consequences of the war and the forces it unleashed.

“They have paid the greatest price for the most serious foreign policy calamity of the last 60 years.

“The apology is also owed to the families of those soldiers who died in Iraq or who have returned home injured or incapacitated.

“They did their duty but it was in a conflict they should never have been sent to.

“Finally, it is an apology to the millions of British citizens who feel our democracy was traduced and undermined by the way in which the decision to go to war was taken on the basic of secret ‘I will be with you, whatever’ understandings given to the US president that have now been publicly exposed.”

The decision make a formal apology is likely to prove highly controversial and may worsen Corbyn’s relationship with some backbenchers after he was heavily defeated in a vote of confidence last week. Corbyn was heckled today by Ian Austin, MP for Dudley North, during his Commons response to David Cameron’s response to the Chilcot report.

Speaking at Church House, this afternoon, following a private meeting with some of the families who service men and women who lost their lives, as well as veterans, and bereaved Iraqis, Corbyn said he had apologised to the group for the “disastrous” war and the actions of the last Labour government.

He also repeated his claim that the Labour government “misled” MPs in the run-up to the crucial Commons vote on the war.

“They were misled by a small number of leading figures in the government who were committed to joining the US invasion of Iraq come what may and were none too scrupulous about how they made their case for war.”

Blair today hit back at that suggestion and said the publication of the Chilcot report showed there were “no lies” and that Parliament was not misled.

“There was no secret commitment to war, intelligence was not falsified and the decision was made in good faith,” Blair told a press conference.