Brendan Nelson's rating as opposition leader has slumped to its lowest level since he was elected, a new poll shows.
The latest Newspoll, taken exclusively for The Australian newspaper at the weekend, found voter satisfaction with Dr Nelson has fallen from 33 per cent to 31 per cent.
His dissatisfaction rating is up six points to 48 per cent.
In the preferred prime minister stakes, Dr Nelson slipped two points to 12 per cent, compared to Prime Minister Kevin Rudd, whose rating crept up two points to 68 per cent.
Mr Rudd's satisfaction rating remained unchanged on 58 per cent, with dissatisfaction also unchanged, standing at 29 per cent.
The poll comes after weeks of difficulty for the coalition over its policy on an emissions trading scheme and some Liberal MPs calling for former treasurer Peter Costello to take over the leadership.
But despite Dr Nelson's standing in the polls, broad support for the coalition has remained unchanged.
The coalition's primary vote was up one point to 38 per cent, compared to Labor which remained unchanged on 47 per cent.
The coalition stands at 43 per cent on a two-party preferred basis, compared to Labor on 57 per cent.
Acting opposition leader Julie Bishop says Brendan Nelson's low approval ratings are not being borne out in the polls that matter.
"Opinion polls are one thing but on every occasion that the voters have been asked to cast a vote since the November election there has been a massive swing against Labor," Ms Bishop said.
"In the Gippsland by-election, when both Brendan Nelson and (Prime Minister) Kevin Rudd took a very high profile role, there was a 10 per swing against Labor.
"We've seen a swing against Labor in the Northern Territory and I believe there will be a massive swing against Labor here (in Western Australia) at the next state election."
The result in Gippsland was followed by a swing of around eight per cent in the NT. If there is a swing anything like that in WA the Carpenter government will be thrown out of office.
"(It demonstrates that) when people actually have to focus on the issues and cast a vote they are reflecting their disillusionment and their dismay with Labor governments across the country," Ms Bishop said.
On the Peter Costello issue, Ms Bishop said that while she would like to see Mr Costello on the opposition frontbench, "he made a statement last November and I'm not aware of any change in that statement".