Mo Mowlam has sent an open letter to The Sunday Times in support of Clare Short.
In the letter, she commended the former International development Secretary for shining 'a spotlight on the failures of the government's foreign policy'.
The former Northern Ireland Secretary continued: 'your integrity, shown by your resignation, puts others to shame. Keep going, your supporters are still with you.'
The letter of support comes after Clare Short resigned over a draft UN resolution being discussed at the Security Council. She claimed that it did not give the UN its promised central role in rebuilding Iraq.
In her resignation speech, Short described the British stance as 'totally dishonourable'.
Short also called for Tony Blair's resignation.
In her letter to the former International Development Secretary, Mowlam points out that Clare Short's resignation 'reminds us that no weapons of mass destruction have been found.'
And that 'the United States and Britain have been unprepared for the difficulties in running Iraq after the war and that Britain's diplomacy up to the beginning of the war was instrumental in seriously damaging the United Nations and the European Union.'