Cherie Blair has come under fire after it emerged that a charity fundraising dinner she spoke at is being investigated in Australia.
Mrs Blair's lecture tour in Australia received negative publicity
Mrs Blair was guest speaker at the Melbourne event in February to raise cash for a children's cancer charity.
Although 60% of proceeds from the dinner should have gone to the charity, it received less than 10%.
Tories say Mrs Blair has "sullied" the office of prime minister. Her agents say she raised cash for good causes.
The investigation was sparked after concerns were raised about the amount of funds made by the Melbourne Exhibition Convention Centre dinner for the Children's Cancer Institute Australia for Medical Research (CCIA).
David Cousens, director of the watchdog Consumer Affairs Victoria (CAV), found that just over 8% (£6,729), of the £81,700 raised by the evening was going to cancer research, with £74,900 absorbed in paying for the dinner and guest speakers.
He said the CCIA had breached its registration under Victoria's Fundraising Appeals Act, which states that a charity must receive no less than 60% of funds raised in an appeal on its behalf.
The CCIA had until 27 October to explain why it should stay registered as a charity in Victoria, he said.
"The event that was held which involved Mrs Blair received a degree of publicity and it was followed up with a number of consumer concerns being registered with us," he told BBC Radio 4's Today programme.
"We investigated that and found that just over 8% of what was raised by the function in Melbourne was, in fact, going to cancer research.
"The issue from our point of view as a consumer agency was really whether or not the conditions of registration of the fund-raiser had been adhered to.
"The issue of what was paid to the speaker is not an issue that is at all relevant to us."
Mrs Blair's speaking tour of Australia prompted a host of negative publicity after it was reported she received £100,000 for her engagements.
The investigation prompted shadow Commons leader Chris Grayling to say: "The fact that Mrs Blair's commercial activities have left her exposed to an Australian government inquiry absolutely confirms my view that she has got to stop making money in this way.
"We simply cannot have the office of British prime minister sullied like this."
Downing Street has refused to comment on the matter.
But the New York-based Harry Walker lecture organising agency, of which Mrs Blair is a client, said she spent "an enormous amount of time fundraising for different charities, the vast majority of it unpaid".
While the Melbourne event "didn't raise much money, approximately Aus $500,000 (£212,900) overall was raised for two charities" from Mrs Blair's speaking events in Australia and New Zealand, the agency said.
"We know that both charities were very happy with the outcome," it added.