A federal government move to charge an extra $6 for visiting a bulk-billing doctor would deter almost four in 10 people from booking an appointment, according to the latest budget poll.

The likely introduction of the co-payment would spark a strong voter reaction to a policy being seen as undermining universal health coverage, the Fairfax-ReachTEL survey found.

Around half the 3241 people who took part said they also want Prime Minister Tony Abbott to make further cuts to his parental leave scheme.

The finding comes despite Mr Abbott cutting payments from a previous cap of $75,000 for mothers earning $150,000 a year to $50,000.

The poll also found 68 per cent of voters are against a proposed increase to the retirement age, although a deficit tax attracted support from 54 per cent.

The poll's co-payments finding was based on respondents being asked how they would react to a $6 payment for GP visits, with 39 per cent saying they would be less likely to consult their GP.

If the co-payment was lifted to $15 - a figure recommended by the recent National Commission of Audit - about 63 per cent said they would be less likely to do so.