Tony Blair proposed to Cherie while she was on her knees cleaning a toilet, she has revealed in a BBC One documentary.
Mrs Blair said the toilet-floor proposal had been 'romantic'
In The Real Cherie Blair - being shown on Wednesday - she says Mr Blair popped the question in a "terribly romantic" way while they were on holiday in 1979.
Meanwhile, the ex-prime minister has revealed he sometimes called his wife - a Liverpudlian - "Bolshie Scouser".
The Blairs left Downing Street last week, with Mrs Blair telling reporters: "I don't think we'll miss you."
In the documentary, Mrs Blair denies exploiting her position as prime minister's wife to make money, following claims she was reportedly paid as much as £30,000 for speaking engagements.
Asked by interviewer Fiona Bruce whether people would have been prepared to pay to hear her speak if she was not the prime minister's wife, she said: "I really don't want to answer that question, actually. I don't know what it's got to do with anything.
"There's no way I have exploited my position. I give 120 speeches a year and of those 10 are for payment."
Mrs Blair, a barrister, also revealed she had tried to persuade her husband not to stand down as prime minister.
However, she denied having branded his successor Gordon Brown a liar during his speech at last year's Labour conference, insisting she expected him to be "a fantastic prime minister".
Mrs Blair described the furore over convicted conman Peter Foster's involvement in her purchase of two flats in Bristol as "a fuss about nothing" and defended her friendship with his then girlfriend Carole Caplin.
She denied media stories that she had shared a mud-bath with Ms Caplin in Mexico and that the former model had made her obsessed with New Age healing therapies.
"I am not bonkers," she said. "How could I be a successful QC and be that completely stupid?"
Mrs Blair told how Mr Blair had proposed to her while they were on holiday in Tuscany in 1979, before he became an MP.
"As we were leaving to go home, I was cleaning up in the bathroom," she recalled.
"I'd cleaned the toilet and he suddenly announced, while I was on my knees, that maybe we should get married... It was terribly romantic!"
But Mr Blair gets his own back with a personal revelation about his wife: "Bolshie Scouser is sometimes what I call her when she's holding forth, which she can sometimes do."
The Real Cherie Blair will be broadcast on BBC One at 2100 BST on Wednesday.