Home Office minister and Southampton MP John Denham has become the third government minister to resign over the Iraq crisis.
Mr Denham criticised "American unilateralism" in his speech
In his resignation speech to the House of Commons, the MP for Southampton Itchen said he resigned as he could not vote with the
government on plans to go to war.
He criticised United States "unilateralism" and said he could not support military action when there was no international consensus.
Mr Denham's resignation comes after Leader of the House of Commons Robin Cook and the health minister Lord Hunt stepped down over objections to war without a fresh United Nations mandate.
Mr Denham said: "For me this has been about...whether we can put our hands on our heart and say the greater part of those who should be supporting us do so.
I have constituents in our armed forces in the Gulf..we may have failed them, I doubt they will fail us
"I do not believe they do.
"I do not fault the Prime Minister for this, no-one could have worked harder to forge that consensus."
When heckled by William Hague during his speech, Mr Denham said:
"I will not give way to the honourable gentleman - I've never made a resignation speech before and I'd rather like to get to the end of this one", to laughter from the house.
"I have constituents in our armed forces in the Gulf...if they are by the vote of this house committed to fight, I stand with them - we may have failed them, I doubt they will fail us."
The former Christian Aid and Oxfam worker was appointed Minister of State for the Home Office in June, 2001, after serving as Southampton Itchen's MP since April, 1992.
Mr Denham joined the Home Office from the Department of Health just after the
June 2001 general election.
'Man of principle'
The 49-year-old former city councillor first won his Southampton Itchen seat on his third attempt.
Leader of Southampton City Council June Bridle said: "Speaking personally, I
applaud John for his principled stand.
"He has made his personal views on the
current Iraq situation known and he has made an enormous personal sacrifice."
Earlier in his political career, Mr Denham was a campaigns officer for the charity War on Want from 1984 until 1988.
He then spent a further four years as a consultant to development charities and other agencies.
He later served as a Hampshire county councillor from 1981 until 1989 before becoming a city councillor from 1989 until 1993.