Cherie Blair's decision to make a speech on life in Downing Street for a £30,000 fee was "outrageous" says ex-Cabinet minister Clare Short.
Mrs Blair had "crossed the line", she said, adding it was one thing to pursue her career as a lawyer but getting cash for being the premier's wife was wrong.
On Tuesday Mr Blair showed exasperation over the row as he defended his wife over her decision.
Her talk in Washington coincided with his pre-G8 meeting with George Bush.
Senior Tory MP Tim Yeo meanwhile accused Mrs Blair of being part of the "gradual corruption of the integrity of public life".
Ms Short, a former international development secretary, made her comments during an appearance on BBC TV's The Daily Politics.
She said: "[Mrs Blair] was allowed to be a lawyer and earn her living as a lawyer and she's a well paid lawyer - that's her independent profession, but to be getting money for herself personally out of being the wife of the prime minister is wrong...".
'Coincidence'
The Tories have urged Mrs Blair to hand her £30,000 fee for the lecture on life inside Downing Street to charity.
Mrs Blair said the fact her speech came at the same time her husband was in the US was a coincidence.
She said she had to "walk a tightrope" with her joint roles as a professional woman and as the UK prime minister's wife.
She told a US interviewer her engagement had been booked well in advance, adding: "It has crossed my mind that of all the 365 days in the year that Tony could have come, this was not my favourite."
She went on to say "you can't please all the people all the time".
Ministerial code
Mrs Blair argued that Denis Thatcher had a number of "outside interests" and "no-one found anything wrong with that".
The row centres on Mrs Blair's decision to give a talk on Tuesday at Washington's Kennedy Centre - billed as the inside account of the "First Lady of Downing Street".
The Conservatives say the lecture went against the spirit of the ministerial code which prevents members of the government making money from commercial activities relating to their job.
Shadow Commons leader Chris Grayling says the code should cover activities directly linked to the job of the Prime Minister.
Mr Grayling said Mrs Blair should donate any fee to charity arguing the "commercial nature" of her trip was "inappropriate".
'Normal procedure'
He said: "What is wrong to me is the Blair family making tens of thousands of pounds out of effectively exploiting Mr Blair's job when the ministerial code says they are not allowed to do that."
And he has written to Foreign Secretary Jack Straw saying he is "astonished" Britain's ambassador was involved in Mrs Blair's private engagement, after Sir David Manning introduced Mrs Blair at the Kennedy Centre.
"I should be grateful if you could investigate what has happened and in particular why a senior civil servant would agree to participate in a purely commercial event on behalf of Mrs Blair," he writes.
But Downing Street said it was "normal procedure" for Sir David to introduce or accompany "any prominent British citizen visiting Washington".
2012 ambassador
The Foreign Office said Sir David had introduced TV chef Nigella Lawson and artist Andrew Goldsworthy when they were in Washington.
The spokesman added that on the day of Mrs Blair's speech the ambassador also introduced the headteacher of the local British school in Washington.
A spokesman for London 2012 said: "Cherie Blair, as a senior bid ambassador, has undertaken a series of briefings with the international media and we were delighted that she was able to meet and brief senior figures from the American media while in New York."
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