Bernardi to overshadow parliament start

Federal parliament finally returns after the long summer break but Malcolm Turnbull won't be getting the clean slate he may have hoped for.

The prime minister will start the day by attending the traditional first-day-back church service - a brief moment of peace ahead of what may be a dramatic day.

Mr Turnbull is expected to start the parliamentary year with a defection on his hands, with conservative backbencher Cory Bernardi expected to quit the coalition to start his own political party.

The new party would be based on his Australian Conservatives movement, which already has more than 50,000 members.

Cabinet minister Arthur Sinodinos insists it won't be a distraction for the government on its first day back in Canberra.

"Not if we and the press focus on what's important to our fellow Australians," he told ABC radio.

"The decisions of one individual are not necessarily the fault or the responsibility of others."

It comes as the coalition's primary vote support went backwards in Newspoll - down to 35 per cent and its lowest level since Malcolm Turnbull toppled Tony Abbott as prime minister.

Senior frontbencher Greg Hunt denied Mr Turnbull's job was at risk.

"I believe deeply in the work that Malcolm Turnbull is doing," he told ABC's 7.30.

He hoped Senator Bernardi would honour his pledge to the Liberal Party and voters.