Cherie Blair’s former aide this week defended state schools against charges they were failing.

Fiona Millar, who left her pound;58,000-a-year job in Downing Street last week, told The TES: “Lots of people use the state education system and are very happy with it.

“It is depressing to see a small number of people who do not use state schools talk them down.”

Ms Millar, who has three children aged between nine and 15 in state schools, said: “I am very happy with state education. I am no different from any other parent or governor who has children going through the system.”.

The partner of Tony Blair’s ex-spin doctor Alastair Campbell was due yesterday to take part in a public debate about the effectiveness of the comprehensive system in a head-to-head with Chris Woodhead, the former chief inspector of schools.

Both she and Mr Campbell are keen advocates of the state education system.

Ms Millar was Mrs Blair’s principal media adviser and is now planning to re-establish her career in journalism.

She said she wanted to defend state schools against the claim that they were a “comprehensive disaster”. Ironically, Mr Campbell provoked anger two years ago when he pronounced that “the day of the bog-standard comprehensive is over”, as the Government unveiled its plans for more specialist schools.

Heads complained that he had damaged the image of the comprehensive system.

Earlier this week Ms Millar gave an interview to the BBC’s The Politics Show in which she attacked government policy, including league tables which she said were an “artificial way of looking at what inner-city heads were achieving”.

She also called on the Government to abolish charitable status for private schools. She said it was impossible to justify the pound;82 million a year benefits the sector received when so many state schools needed more money.

Ms Millar also attacked the “two worlds” of state and private education, and said that parents who chose fee-paying schools were “certainly depriving the state sector of very articulate voices”.

“A thriving comprehensive school would benefit children from all backgrounds and all areas. There are parts of London where there’s little ‘buy-in’ from what you describe as the the elite into the system. That has a knock-on effect for the children in the schools that are left behind.”

She added that if all parents used state schools “they would have a stake in the improvement of the state sector, which the rest of us want to see”.

However, she doubted any government would actually abolish private schools.

“I think it’s extremely unlikely for any government to tackle that section of middle England by getting rid of private education,” Ms Millar added. This week’s debate and interview were not Ms Millar’s first foray into the world of education.

In July she told friends privately that she planned to speak out about the shortcomings of the Prime Minister’s schools policies once she had left her post, despite being a member of the inner sanctum of advisers to the Blairs.

She also attacked the Government for not doing more to avert the schools funding crisis.

Ms Millar, who is chair of governors at her children’s primary school, Gospel Oak, in Camden, North London, wrote to parents calling on them to lobby ministers over the issue, which arose because of changes to funding formulas and increases in the costs of employing teachers.

The school faced losing teachers and support staff after costs rose 20 per cent, but its budget increased by just 7 per cent.

She said in her letter that “the Government has not thought through the implications of its changes for some of the neediest schools, such as those in inner London”. This week Ms Millar repeated her belief that schools needed more cash.

She said: “It is very disappointing that some schools like ours have not got as much money as expected this year. But it is a complicated issue and I would like to see what the Government comes up with to resolve this problem.”