A drop in Prime Minister Kevin Rudd's approval rating in the latest opinion poll has prompted commentary on the future Labor leadership.

Mr Rudd's voter satisfaction rating has slumped to its lowest level since he became Labor leader.

The Newspoll in the Australian newspaper shows 48 per cent of voters are satisfied with Mr Rudd's performance, while 41 per cent are dissatisfied.

It is the first time Mr Rudd's rating has dipped beneath 50 per cent as prime minister; the two-party preferred figures remain the same at 52 to 48 per cent in favour of Labor.

Labor backbencher Darren Cheeseman has backed Mr Rudd but he has pointed out that the deputy, Julia Gillard, is waiting in the wings.

"She is naturally in line to become the prime minister at some point into the future," he said.

Opposition frontbencher Ian Macfarlane has tried to stoke leadership tensions.

"If I was Kevin Rudd I wouldn't sleep with both eyes shut," he said.

Prime Minister Kevin Rudd has told ABC Local Radio he thinks it will be a close election.

"It'll be a hard-fought election and I expect that but I will simply continue in the business of ensuring that we are keeping the economy strong," he said. "It'll be a tough fight and that's what I fully expect come election time."

Meanwhile, the poll shows the Opposition's paid parental leave scheme is failing to gain traction with voters.

The poll comes as former prime minister Paul Keating launched an attack on Opposition Leader Tony Abbott, labelling him an "intellectual nobody" with no policy ambition.

Speaking on ABC Radio National today, the former Labor prime minister gave a scathing assessment of Mr Abbott's performance, saying he had consolidated the right-wing "nutters" behind him.

And he took exception to Mr Abbott's criticism of Indigenous acknowledgment and welcome to country ceremonies at official functions by calling him a "little John Howard".

Mr Abbott won the leadership from Malcolm Turnbull last December after urging the party to reject Mr Turnbull's climate change policy.

And he opened up a new front in the culture wars yesterday by claiming that acknowledgment of Indigenous elders at official functions was paternalistic and tokenistic.