Clare Short's fellow Birmingham MP Dr Lynne Jones has said "the Downing Street club" was "going for" the international development secretary.
Dr Jones thinks Ms Short 'jumped before she was pushed'
Ms Short announced her decision to resign from the cabinet shortly after 1000 BST on Monday.
Dr Jones, the MP for Birmingham Selly Oak, told BBC News 24 that "the Downing Street club were going for her in this kind of less-than-subtle way.
"I guess that she probably jumped before she was pushed."
Dr Jones said the Birmingham Ladywood MP's position has been untenable for some time.
"When she made her statement about the war I thought she was spot on.
"And indeed, in the aftermath, she has been proved right in terms of the humanitarian situation and the lack of preparation.
"But I guess, following all the briefings against her, for instance in relation to the foundation hospitals vote last week, the writing must have been on the wall for her.
"That the Downing Street club were going for her in this kind of less-than-subtle way, but a way that's fairly obvious to those observers of the political scene."
Asked if she felt betrayed by Ms Short for not resigning after her outburst about the Prime Minister's "recklessness" prior to the Iraqi war, Dr Jones said: "I long since ceased having those strong feelings about Clare.
"There's been this portrayal that she's a representative of the left and she may have been a long time ago, but I don't think that's the case now.
"She's a woman who clearly cares a great deal about ordinary people and about the job that she's doing and it has been very difficult for her to balance those principles with the pragmatism that's perhaps required to be within the Blair government."
West Midlands Labour party chairman Peter Lightfoot said Ms Short was an outstanding international development secretary.
"She was highly regarded both nationally and internationally.
"She is also highly regarded as constituency MP in Birmingham Ladywood and held in high esteem in the city of Birmingham and in the West Midlands region."
Ms Short worked closely with the organisation Islamic Relief, in Birmingham, which delivered aid to post-war Iraq.
Adeel Jafferi, from Islamic Relief, said Ms Short would be greatly missed by the organisation.
"The international aid organisations around the world will miss her but they'll be ready to work with whoever takes over from her and I'm sure her department will run very efficiently, albeit without her."