Tony Abbott has given a strong signal his government won't exempt pensioners from its planned $7 GP co-payment.

The prime minister argued pensioners were not exempt from making a co-payment on taxpayer-subsidised medicines.

"Why should they be exempted from the Medicare co-payment?" he told Fairfax Radio on Wednesday.

The government is locked in negotiations with doctors and Senate crossbenchers with the amount and scope of the co-payment a major sticking point.

"If it's right and proper to have a modest co-payment for the PBS, why not have a modest co-payment for Medicare, too?" Mr Abbott said.

He refused to say how the talks were going, but is confident parliament will eventually pass a modest co-payment.

As for the precise detail of any agreement?

"Let's wait and see how we go with our discussions with the AMA and crossbench," Mr Abbott said.

Labor says no amount of fiddling will fix the "unfair, regressive and bad" measure.

"Any compromise ... will be nothing more than a cynical political fix by a desperate government," opposition health spokeswoman Catherine King said in a statement.