Opposition Leader Tony Abbott has contradicted comments made by his education spokesman, saying all states need to sign up to Labor's school funding reforms before the Coalition backs the plan.

''You cannot have national change unless all states are on board,'' he told reporters in Melbourne on Thursday.

Earlier, opposition education spokesman Christopher Pyne said the Coalition would honour the Gonski reforms if there was ''overwhelming support'' from states and territories.

''If the government can get most of the other states to join … we will obviously keep this new measure, but they are a long way from achieving that,'' Mr Pyne told ABC Radio.

Mr Abbott said it would be impossible for Labor to meet the conditions put forward by the Victorian government.