Two more government frontbenchers are expected to resign over the weekend, leaving Scott Morrison's ministry team even further depleted just weeks out from an election.

Defence Minister Christopher Pyne has not denied speculation he will quit on Saturday, while Defence Industry Minister Steve Ciobo has also remained silent amid reports he has pre-recorded a television interview in which he confirms his retirement.

"I don't want to add to the speculation," Mr Pyne told reporters in Adelaide on Friday.

"What I need to do is keep representing my constituents as well as I've tried to in the last 26 years.

"As I've said before, I don't believe in unnecessary by-elections."

The prime minister has already lost frontbenchers Kelly O'Dwyer, Michael Keenan and Nigel Scullion, who will retire from parliament at the May poll.

Mr Morrison was asked if he had spoken to the frontbench pair about their impending decisions, and did not deny Mr Pyne or Mr Ciobo could be about to quit.

"I talk to them all the time," Mr Morrison told reporters in Townsville

"There's a lot of speculation going on, isn't there?"

Mr Morrison also denied he had intervened to push the pair's announcements off until the weekend.

Mr Pyne joked about his future with his TV colleague and Labor defence counterpart Richard Marles on the weekly Sky News show they host together.

"Once I decide to announce my retirement, you'll be the first to know," Mr Pyne told his co-host.

Mr Marles praised Mr Pyne for his time in parliament, which began with his election in 1993.

"If it is true, yours has been a mighty career and I for one will miss you. I'll probably get in trouble for saying that, but that's just how I feel," Mr Marles said.

Mr Ciobo, an 18-year parliamentary veteran, tweeted on Friday he was looking forward to travelling to Indonesia within days to sign a landmark free trade agreement.

The Queenslander was demoted from the trade portfolio after the August leadership spill, in which he ran for deputy.

A Queensland Liberal source told AAP he would be "surprised" if Mr Ciobo retired from parliament as he was currently very active in fundraising for the election campaign.

If he leaves his safe seat of Moncrieff on the Gold Coast, it could open up a landing spot for Peter Dutton, who is facing a battle to hang onto his seat of Dickson.

Labor leader Bill Shorten said the resignation speculation showed the government had given up.

"I say to Australians, if the ministers in the government are giving up on the government, you should too," he told reporters in Sydney.