Prime Minister Tony Abbott has defended his decision to slash government rebates for short doctor visits, saying it’s what the Australian Medical Association wanted.

The government has come under fire for its changes to GP fees which, according to doctors, could see patients patients paying up to $20 more for an average visit.

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But Mr Abbott’s chances of pushing the changes through became more difficult on Wednesday when Labor declared it would oppose the  “sneaky” pre-Christmas change to the rebate system for GP visits.

Opposition Leader Bill Shorten says the party will move to disallow the change to rebates.

The government tabled the change as a regulation before Christmas, so it could be overturned after the Senate returns on February 9.

Mr Shorten called it a Christmas attack on the Medicare system.

“Everyone knows that the Abbott government pull the old political trick of bypassing Parliament, of rushing a regulation in before Christmas, then they change their Health minister, then they’ve gone on holiday and they expect Australia to swallow their shoddy, shonky broken promises,” Mr Shorten told reporters in Queensland.

But Mr Abbott said the new payment structure was designed to encourages doctors to spend more time with patients by cutting rebates for visits under six minutes.

“Just a few months ago the AMA was saying that they didn’t want to see six-minute medicine, they didn’t want to support bulk billing, they wanted to see doctors spending more time with their patients, and that’s exactly what these changes are designed to produce,” Mr Abbott told Fairfax radio on Wednesday.

The Greens said they plan to disallow the reforms in the senate, as will cross bench senators  Jacqui Lambie, Nick Xenophon and Rick Muir, who have indicated they are unhappy with the proposal.

Mr Abbott suggested they come up with an alternative of their own.

“I say to all of the critics: If you don’t like what we are doing, come up with your alternative because we simply cannot go on as a government, and as a country, living beyond our means,” he said.

The changes include a $20 cut to the Medicare rebate for GP Level B consultations lasting under 10 minutes, from $37.05 to $16.95, to start on January 19.

A further $5 cut to GP rebates comes in from July 1, on top of a near-six-year freeze on Medicare rebate indexation.

The AMA believes these changes will lead to increased out-of-pocket expenses for patients and higher health costs as more people turn up to hospital emergency rooms.

– with AAP