Parents could be given vouchers towards their child's independent schooling under a Conservative government, the shadow chancellor has said.

Oliver Letwin signalled that while high profile institutions such as Eton will not be subsidised, allowances would be given to parents for private schools where fees "cost slightly more than the maintained sector".

"That is an area we are currently looking at," he told the Independent. "We do not envisage it being used for Eton. We are clear that you will not be able to use the passports as a contribution to an expensive public school."

The proposed "passport" system was unveiled by the Conservatives during their autumn conference last year by then-shadow education secretary Damian Green.

Letwin's comments suggest that the move could also apply to schools where the fees were above the £3,500 a year estimated cost of state education.

However, the move is said to have split the shadow Cabinet - while some believe the idea will encourage the creation of new independent schools charging lower fees, others warn it could be difficult to "draw a line" between lower-fee schools and those charging higher rates.

Attack

The government has also attacked the idea.

"This proposal is even more extreme than the reviled assisted places scheme," said education secretary Charles Clarke.

"It would extend support from the taxpayer to all parents who send their kids to private school. In a world of tight resources, this will never be a priority for a Labour government.

"It is every child who matters to Labour, not just a privileged few."

Taxation

In the same interview the shadow chancellor also pledged that any tax cuts included in a Conservative election manifesto would be aimed at the poorest in society.

"There is clearly a strong feeling in the party, which I personally very strongly share, that giving people the ability to choose schools and hospitals and get the degree of control over their own lives that people with more means currently have - does extend also to tax," he said.

However, Letwin gave no guarantees as to by how much taxes would be cut.

"If there is a vast black hole, that will mean it will take us a long time before we can start reducing taxes," he said.

"If, on the contrary, it is a modest black hole, then we may be able to start reducing taxes early."

A lot depends on the actions of chancellor Gordon Brown, Letwin added.

"The worse his mistake, the more constrained we are," he said.

"But also the more necessary our programme becomes and the higher his tax rises will be. The amount of overdraft you have influences how many holidays you can take."