Ruth Kelly, the Education Secretary, hit the airwaves today to defend a "brainstorming" idea from Tony Blair that parents should be forced to stay at home with unruly children thrown out of school.

The Prime Minister made the suggestion in a letter to Sir Alan Steer, a headteacher who chairs the Government's new school discipline taskforce before a meeting with the group later today.

In his letter to Sir Alan, Mr Blair said suspension from school must be seen as "a serious punishment" by both pupils and their parents.

"I would be grateful for your views on how we might reinforce this," he wrote to Sir Alan, who is head of Seven Kings High School in Ilford, Essex. "Should we legally require suspended students to stay at home, accompanied by a parent, rather than allowing them freely to cause a nuisance on the streets or in shopping centres?

"It is clearly essential that parents fully accept their responsibilities if we are to improve discipline and respect in schools."

The proposal was criticised by opposition parties and questioned by teachers unions and parents groups, who said that the idea might be politically attractive but would be hugely impractical.

"Legally, how are you going to enforce this? Is there some sort of house arrest or control order system?" asked Ed Davey, the Liberal Democrat education spokesman.

"In these sorts of situations, the relationship of the parents and the child involved may have broken down and there may be real problems. I think actually punishing the parent and getting them into trouble with their employers could make it worse."

But in a series of media interviews, Ms Kelly said that the idea was only at the "brainstorming" stage and would not be pushed through without the support of teachers.

"Everyone knows parents are responsible for their children’s behaviour out of school. What we’ve now got to do is restore the link between parents and their children’s behaviour in school," she told BBC Breakfast.

"And one way we might do that, for example, is thinking about how parents can become more responsible for looking after their children once those children are excluded and suspended for a few days."

Mr Blair’s intervention in the debate on school discipline follows months of political campaigning over the issue, which was described as a key priority for both major parties in the run-up to the general election in May.

Asked whether the proposals had been thought through, the Education Secretary replied: "I think most of your listeners and viewers would think it pretty commonsense that, where a child is suspended from school, that they don’t regard it as some sort of unofficial holiday where they can go down to the shopping centre and create havoc.

"That actually a parent should take responsibility for that and make sure it’s at home and indeed to make sure that child is learning, if there’s work set by the school."

She added that parents who refused to comply with orders to stay at home with their suspended children could be forced to attend parenting classes or even face fines. "What is important is that parents back the heads," she said.

Chris Keates, General Secretary of the NASUWT, the country's biggest teachers' union, told Times Online that the Prime Minister's suggestion showed that he wanted Sir Alan's group to "think outside the box" and parents to take notice of the issue.

But she said the specific suggestion would raise as many difficulties at it solved, especially for parents who could not afford to take time off work or might be penalised by their employers for doing so. "I would take the Prime Minister's suggestion as underlining the need for parents to be responsible rather than being the only or a practical solution to the problem."

Tony Halpin, Education Editor of The Times, said that the practical difficulties raised by Mr Blair's suggestion would be enormous given the number of suspensions every year - and it failed to address the "hardcore" problem of parents who really did not care what their children got up to.

"It's not quite clear how you would enforce it. When a child is suspended would a teacher be expected to go around to the house and check that they're there, with a parent, or would a police officer do so?" Halpin asked. "Two hundred thousand children were suspended last year so that's a lot of visits."

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