Mo Mowlam has praised Clare Short's "integrity" in deciding to resign from the Cabinet.

In an open letter to Short published in the Sunday Times, the former Northern Ireland secretary said she had "done the right thing" in resigning over Iraq.

She also comforted her former colleague with the prediction that "soon you will be back, either in the government or in some international position".

Mowlam added that her position on the backbenches "is a waste".

Like Short, Mowlam had a difficult relationship with Downing Street during her Cabinet career, which ended in 2001.

Short resigned as international development secretary last week over claims that the prime minister and foreign secretary has given her false assurances over the post-war reconstruction of Iraq.

Mowlam said Short had "shone a spotlight on the failures of the government's foreign policy".

She warned her to expect "bad-mouthing" from former colleagues as a revenge for the embarrassment she caused the Cabinet in her resignation speech last week.

Despite claims that Short had jumped from government before she was pushed, Mowlam insisted that the outspoken Birmingham MP had put principle first.

"Your integrity, shown by you resignation, puts others to shame," she wrote.

And she urged Short to continue campaigning for what she believed to be right.

"Keep going, your supporters are still with you," Mowlam advised.

A former Tony Blair favourite, Mowlam fell foul of the Downing Street machine during her stint in Belfast and was moved to the less vital Cabinet Office.

Echoing Short's condemnation of Blair's "people who live ion the dark", she claimed to have been briefed against behind her back.

Since leaving government at the last general election Mowlam has become increasingly critical of the Labour government, particularly on Iraq.

She backed Short's pre-war claim that the prime minister was being "reckless" in his pursuit of a solution to the crisis.

"The mistakes have been legion and have followed on from each other so quickly that it is good to take stock of them," she wrote in her letter.

Short's resignation "reminds us that no weapons of mass destruction have been found, 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", she went on.

Over the weekend the backlash against Short continued with Charles Clarke accusing her behaving like a "dictator" while in office.

The education secretary argued that Short was wrong to accuse Blair of governing by "diktat".

"I disagree with her picture of policy-making in government completely," he said.

"In all my experience that is completely not the case. The only area I'm not certain if that is true is the Department for International Development when Clare was running it."