A senior government MP has announced his retirement as the polling gap tightens between the Coalition and Labor.

Veteran Queensland MP Ian Macfarlane has decided not to contest his seat of Groom at the next election after 18 years in parliament, nine of which he spent as a minister.

Mr Macfarlane missed out on a ministerial job when Malcolm Turnbull ousted Tony Abbott for the Liberal leadership in September.

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He then sought to join the Nationals, which was endorsed by his local party members but thwarted by state party officials.

“When you’ve become a passenger it’s time to get off and let someone else drive … sitting on the backbench wasn’t an option for me,” Mr Macfarlane told ABC radio on Monday.

Six Liberal MPs and two Nationals have signalled they won’t contest the election due around September, with nine ALP members also retiring.

The deadline for NSW Liberals wanting to recontest their seats is this Friday.

The latest Fairfax-Ipsos poll shows the Coalition’s two-party-preferred vote falling four points to 52 per cent and the Prime Minister’s personal rating dipping five points to 64 per cent.

Asked about the polls, Prime Minister Malcolm Turnbull said the government was providing the economic leadership that voters wanted.

Malcolm Turnbull downplayed the latest poll results.

“We’ve got a strong, diverse economy. We’ve got a confident, capable government,” Mr Turnbull said while campaigning in marginal north Queensland seats on Monday.

Opposition Leader Bill Shorten said voters were responding to the fact that Mr Turnbull was turning his back on issues he had previously supported, such as climate change and same-sex marriage.

“Increasingly he is becoming seen as all talk and no go,” Mr Shorten told reporters in Melbourne.

With Trade Minister Andrew Robb set to retire, human rights commissioner Tim Wilson has quit his role to contest Liberal preselection in Mr Robb’s seat of Goldstein.

Mr Wilson said he wanted to be part of delivering reform, not simply advocating for it.

As Mr Turnbull’s new frontbench was due to be sworn in on Thursday, the incoming Special Minister of State Mathias Cormann said he would pursue Senate voting reform as one of his priorities.

Senator Cormann said if the government settled on changes they would be released “in good time” before the next election.

He said the basis for any proposed change would be the findings of a multi-party parliamentary committee.

The committee called for a system in which “below the line” voters only need to preference as many candidates as there are vacancies, not number every box.

Voters casting a ballot “above the line” could preference candidates, instead of just having to vote “1”.

Labor’s electoral spokesman Gary Gray said his party had a “divided view” over the changes, but the prime minister should meet with Mr Shorten to discuss a way forward.

-AAP