* Two recently elected Queenslanders join frontbench
* Move comes a month after weak showing at Queensland state poll
* Reshuffle targets a younger generation of conservative voters

Australian Prime Minister Malcolm Turnbull on Tuesday named a new attorney general and promoted two junior lawmakers from rural Queensland state to his cabinet in a reshuffle he hopes will bolster his flagging popularity.

Australian leaders often revamp cabinets before the start of a new year but for centre-right Turnbull the move is an attempt to salvage his leadership, ravaged by dismal opinion polls.

Last month, Turnbull's ruling Liberal-National coalition made its worst showing in a Queensland election in more than a decade, when it won 34 percent of the vote as Pauline Hanson's populist One Nation clawed into its conservative base.

A large number of marginal seats in the country's third most populous state of Queensland often give its voters a crucial say in deciding federal elections.

The reshuffle was sparked by the resignation of Attorney General George Brandis from the Senate. Turnbull said he would ask Brandis to be the country's next High Commissioner, or ambassador, to the United Kingdom.

Turnbull gave cabinet positions to Queenslanders John McVeigh and David Littleproud, who both took office 18 months ago.

He dropped infrastructure minister Darren Chester, from the urban state of Victoria, giving the portfolio to deputy prime minister Barnaby Joyce, the leader of the Nationals, which features prominently in Queensland.

‘It's a ministry that showcases the depth of the Liberal and National team, with well-earned promotions for talented individuals, a number of young and upcoming MPs bringing new skills and energy to the frontbench,’ Turnbull told reporters in Sydney.

Asked why he removed Chester, whose duties included running the Australian part of the fruitless search for missing Malaysia Airlines flight MH370, Turnbull said his cabinet had ‘to take into account matters of geography’, but did not elaborate.

The pitch to voters in the northeastern state of Queensland was obvious, said Stewart Jackson, a specialist in Australian politics at the University of Sydney.

‘Everybody's been spooked by One Nation,’ Jackson said. ‘The emphasis will shift back towards Queensland where the National Party was traditionally strong.’

The overhaul also brings youth into a government that has narrowly retained its razor-thin majority in parliament after a constitutional crisis triggered a series of by-elections.

The two promoted Queenslanders, Littleproud and McVeigh, are 41 and 52 respectively. The new attorney general, social services minister Christian Porter, from the iron ore-rich state of Western Australia, is 47.

Employment minister Michaelia Cash, who takes the expanded title of minister for jobs and innovation, and Nationals member Bridget McKenzie, who joins cabinet as minister for sport, rural health and regional communications, are also 47.

Turnbull gave no reason for the departure of Brandis after 17 years, but called him a ‘stalwart’ who had backed tougher national security laws and the legalisation of same-sex marriage, a measure parliament passed this month.

In 2015, when Turnbull unseated then prime minister Tony Abbott, he said the move was necessary because Abbott's government had lost 30 opinion polls in a row. Under Turnbull, the government has lost 25 opinion polls in a row.

Many commentators say that if the figure reaches 30, which could happen as soon as March, Turnbull's party may consider removing him.