Cherie Booth QC: Mother, lawyer, lover, sage. Can Mrs Blair, Superwoman, do it all?

Critics claim she uses her position as the Prime Minister's consort to boost her professional career. But she doesn't see any conflict

In the summer of 1997, at a children's party to mark the 10th anniversary of the Wishing Well Appeal at Great Ormond Street Hospital, the new Prime Minister – having dutifully sung "Happy Birthday" – was handed a big cake. Mr Blair just stared at it. Mrs Blair stared at him. Eventually, she got a knife, cut it up and gently instructed her husband to hand it out to the children.

She was Mum at the tea table, knowing wife and spin doctor, all in one. Displaying an instinct for people and politics, Cherie Blair – advising, then standing back while the Prime Minister got on with the job – was the perfect consort. Now such a gesture would be viewed with suspicion, as evidence of the power dynamic in the Blairs' relationship: he, the compliant figurehead; she, the power behind the throne.

The first "First Lady", as the papers proudly proclaimed her after Labour's landslide victory, has now been branded the "Tsarina" following a brief period in which her detractors insisted that she was a "cross between Hillary Clinton and Lady Macbeth".

The latest outcry was prompted by reports last week that Mrs Blair had been hosting "political" events at Downing Street. In fact, she has been introducing guest lecturers at No 10 and chairing the question-and-answer sessions that follow since 1999. And, say her aides, she will continue to do so. Another is scheduled for tomorrow night.

"She feels completely non-defensive about it," her aide said. "On the whole, until now, the press have been very fair to her but for some reason it's 'get Cherie week'. This is unfair because it's a complete misrepresentation of the facts. But we'll have to live with it."

Opponents of the New Labour regime have made much of the fact that Mrs Blair is "unelected and unaccountable" – charges that were defended by similar people when they were levelled at the House of Lords. Others have focused on an apparent conflict of interest with her profession: she is a QC and a part-time assistant recorder who wants to become a judge. The independence of the judiciary from the executive is sacrosanct in the UK's unwritten constitution. There was also anger at her decision to hold professional consultations in Downing Street and to head her notepaper "Cherie Booth QC, 10 Downing Street".

But Mrs Blair's career, at a deeper level, has always been part of the burgeoning "Cherie problem". As Cherie Booth QC, the Prime Minister's wife is an eminent human rights lawyer. Always a high flyer, she got a first-class degree from the London School of Economics and in 1976 came top in her Bar exams. Colleagues regard her as "brilliant", "at the top of her profession" with "commanding advocacy skills".

Her legal career has, on occasion, brought her into conflict with the Government led by the man she met in the chambers of Derry Irvine (now the Lord Chancellor), while taking her first steps towards becoming a barrister. Earlier this year she took a case against the Ministry of Defence on behalf of 100 former Army officers fighting age discrimination. And in a high-profile case, she represented the TUC in a legal battle against government policy over the right to take parental leave. It has not all been one-way traffic, though. Ms Booth, in a newspaper article in 2000, launched a passionate defence of the much-criticised Human Rights Act.

She is unique in being a working woman who also happens to be the Prime Minister's wife. She will never be like Denis Thatcher, walking two steps behind his spouse, or like Norma Major who preferred Huntingdon and Chequers to life above the shop; let alone like Mary Wilson, wife of the former Labour Prime Minister Harold Wilson, though the two are confirmed friends. She is adamant that her work, albeit with a diminished caseload due to her other duties, will remain a priority. "She's an extremely intelligent woman. If she were doing only the official duties of the Prime Minister's wife she'd go a bit potty," a friend said.

Work comes second only to the family. Mrs Blair, a "superwoman" role model as one survey of teenage girls had it, is devoted to her husband and children. Of that there is no doubt. But the public interest in the Blairs is such that they have rarely been able to enjoy an entirely private life.

She has had to cope with unwanted publicity over a decision to send her sons to the grant-maintained Oratory School, and eldest son Euan's drunken binge in Leicester Square (and his subsequent misbehaviour in an Italian hotel). More recently, she has had to cope with the has-he-hasn't-he row over baby Leo, the latest addition to the Blair brood, born when Mrs Blair was 45, and the controversial MMR vaccine.

Linda McDougall, author of the unauthorised biography The Perfect Life of Mrs Blair – herself the wife of a Labour MP – is unsympathetic. "We are all entitled to a private life but not if we up the stakes and say we are having a public one. It's hypocrisy," she said.

Although Mrs Blair is determined to protect her four children from press intrusion, she is nevertheless resigned to surrendering much of her own privacy. She is said to hate jibes about her appearance and dress sense: she has been pictured bleary-eyed in her nightie on the morning after the 1997 election; we have seen her "cellulite" in holiday snaps; and on an official trip to South Africa she was branded a "dowdy apparition whose stodgy outfit should be donated to Oxfam".

Everything about her has come under scrutiny, from her new-age crystal around her neck to her expensive Mayfair hairdresser. She has learnt to put up with it, concentrating instead on being a woman in her own right. Ms McDougall, like many, is impressed by Mrs Blair's credentials. "I think she's got lots of strengths. She's very intelligent, she's very determined. She's charming and she's tough. And she's got the combination to succeed." But, says her biographer, the one thing she is not is a "sophisticated politician".

Cherie Booth, the daughter of actors Tony (who left the marital home when she was just a child) and Gale, wanted at 14 to become the first woman prime minister. At 16, she joined the Labour Party in her native Liverpool and in 1983 stood unsuccessfully in Thanet North, a safe Tory seat.

Friends say that a pact dictated that at the point when Mr Blair won Sedgefield that was the end of her political ambitions. But it was not the end of her political convictions that some still claim are much stronger and better defined than those of her husband. She pursued her own career. He pursued his.

But, as Mr Blair himself said, Cherie is the "rock on which my life is built". His biographer, John Rentoul, put it slightly differently. Referring to Mr Blair's ambitions to take the Labour leadership, he wrote: "The iron had entered Blair's soul ... That iron took the human form in Cherie."

The truth is that Cherie is many women: as Mrs Blair, she is both the Prime Minister's wife, the love of Tony's life and Mum to Euan, Nicky, Kathryn and Leo; as Ms Booth, she is an ambitious and successful barrister.

At an event coinciding with the Labour Party conference in Bournemouth in 1999, she was given a commemorative brick with the name Cherie Blair QC on it. It is the name of a person who officially does not even exist. Some of Cherie's critics claim that she does. But both Mrs Blair and Ms Booth maintain that she never will.