Saint or sinner, why have they got it in for Cherie?

Cherie Blair is not on the government payroll. She is not an elected representative. So why is the Prime Minister's wife increasingly seen as fair game by those who oppose her husband's politics?

The attacks on Mrs Blair have grown over the years since Labour came to power, and resumed last week with a ferocity that none of her predecessors in the private rooms of 10 Downing Street ever had to face. It happened at exactly the same time as the man she married was launching a fight-back against those same critics, having been put on the ropes by coverage of the row with Black Rod.

Watching Mr Blair perform before the cameras at his new presidential-style press conference was like seeing Muhammad Ali duck and dance in his prime. It helps to explain why his opponents, frustrated by their inability to land a serious blow, have taken to lashing out at those closest to him.

But Stephen Byers is a politician. Alastair Campbell is a highly paid political official. The same can hardly be said of Mrs Blair, but that does not stop some people. "If you want to have a go at him, having a go at her is a good way of doing it," says an insider at her bête noire, the Daily Mail.

That has not always been the case. During New Labour's honeymoon after the 1997 general election, Mrs Blair was the darling of the press, a kind of "superwoman". Commentators fell over each other to voice their admiration for Cherie Booth, the successful barrister, who doubled up as the Prime Minister's wife and mother of his three children. When their fourth baby, Leo, arrived Mrs Blair was heralded as a minor medical miracle for giving birth at 45. Downing Street had its first new-born in living memory.

Recent incarnations have been far less flattering, culminating in the venomous response to Mrs Blair's ill-timed remarks about Palestinian suicide bombers last week, hours after an attack that killed 19 people. This serious gaffe came just a few weeks after Mrs Blair had been criticised for hosting policy receptions at Downing Street, and was "just what we'd been waiting for", according to one critic.

Suddenly there was something more substantial to bitch about than Mrs Blair's clothes, her interest in alternative medicines, the behaviour of her teenage son, her refusal to discuss the baby's medical records during the MMR scare or – that most horrific of faux pas – her failure to wear a hat or resist a yawn at the national service of thanksgiving for the Queen at St Paul's.

Richard Littlejohn, the most energetic of her critics, devoted two full-page columns in The Sun last week to the woman he calls the "Wicked Witch". First he rounded on the gaffe, and then he dismissed her swift apology.

Mr Littlejohn, like his fellow Cherie-picker Stephen Glover on the Daily Mail, comes at the issue from a right-of-centre perspective. These men don't like Labour; they don't like Mr Blair so, by definition, they don't like Mrs Blair. Paul Routledge of the Daily Mirror comes from the left. He doesn't like New Labour, doesn't like Mr Blair so, by definition, doesn't like Mrs Blair (though he insists it's nothing personal). The message, however, boils down to pretty much the same thing: keep your mouth shut, love.

The Daily Mail, which has attacked more consistently and with more enthusiasm than any other media outlet, has more complex reasons for doing so. Mrs Blair personifies much of what the Mail disapproves of in the modern female: she is a keen advocate of women's rights; in her legal work she defends human rights; she is "politically correct".

A further explanation is offered by several sources for the personal animosity that Paul Dacre, the paper's editor-in-chief, feels towards her. He was apparently appalled and incensed when Mrs Blair breast-fed baby Leo in front of him during a dinner party in Downing Street in the summer of 2000. The "incident", which took place in front of an aghast Mr Dacre and Lord Rothermere, the Daily Mail's proprietor, is seen as a "seminal moment" in the relationship between the Prime Minister's wife and the paper. "The attacks on her have been more pronounced since then," says a Mail insider, who wants to remain anonymous for obvious reasons. "There are some things she does that make Dacre steam. His voice gets strangulated and he does an odd ape-like dance."

More seriously, Mrs Blair is accused of "hypocrisy" in her attitude to the press. She wants to protect her children from the limelight but then allows her son to be pictured with the film star Kate Winslet, they point out. She wants privacy, then poses with Liz Hurley.

Publicly the Tory party says nothing about Mrs Blair, although senior Conservative sources admit they are asked about her almost every day. Privately, they believe she has "brought it on herself" by being "up-front and political".

Some have compared her to Hillary Clinton, the wife of the former US President, who followed a long line of overtly political First Ladies. They insist such a creature should not be allowed to flourish in Britain. Political spouses should be silent, like Denis Thatcher or Norma Major. Not that the former was ever pictured looking down at his latest suit next to a headline asking: "Does my bum look big in this?".

The charges against Mrs Blair are firmly rejected by those closest to her. While none denies that she has taken a keen interest in politics since joining the Labour Party at 16 (she stood unsuccessfully as a Labour candidate in Thanet North in 1983), friends insist she now leaves party politics to Tony.

As for her treatment by the press: "It doesn't particularly bother her. The only thing that does is when people attack her work or her personal life."

There is some support for Mrs Blair. More than 30 Labour MPs signed a Commons motion to protest at "bullying" of her in the row over the Middle East. And in the week that the Government launched a counter-attack against the press over spin there were some urging the media to grow up. It was time to accept that a woman could be more than a mere appendage to her husband, they said, and that it might be helpful to listen without prejudice to the opinions, on certain issues, of a highly educated, articulate professional.

Jack Straw, the Foreign Secretary, told a private meeting of Labour MPs last week that attacks on Mrs Blair were "sexist". Maybe. If they continue or even get worse they could also be damaging.

Does that mean Mrs Blair will retreat into the shadows never to be seen or heard again? Unlikely. "She has her work, she has her family and after that she has a role as the Prime Minister's wife," says a friend. "She will continue to fulfil that role."