West Australian Premier Colin Barnett will announce a major Cabinet reshuffle after Easter in a bid to revive his Government's stocks, after admitting he was taken aback by polling that has him losing next year's election.

The latest ReachTel poll suggests the Government is looking down the barrel of a thumping defeat at the election in March 2017.

Mr Barnett said the results made him the underdog, and confirmed he would announce a "significant" shake-up of his frontbench after Easter.

He admitted he was a little surprised by the newspaper poll.

"I think it's fair to say it was a good poll for the Labor Party," he said.

"It was a bad poll for the Liberal Party and therefore I believe the Labor Party, at the moment, probably has its nose in front."

Mr Barnett said the electorate was highly volatile and it would be up to him to convince voters he has a proud record to stand on.

"This Government has an outstanding record on the economy.... yes, debt is high at $30 billion — higher than I would want — but you may call it debt, I call it an investment in our future."

Premier finalising new-look Cabinet

Mr Barnett is promising substantial change to his Cabinet, including a number of new ministers and portfolio swaps.

Ministers will be advised whether they are in or out over the next few days.

"I think people are looking to see some refreshing of Cabinet. They're looking for a statement and some shift of responsibilities, so it's quite a significant change," he said.

There is likely to be least three new faces in Cabinet, with the retirement of Kim Hames freeing up one spot and two more vacancies created with Helen Morton and Ken Baston widely expected to be dropped.

"Any minister that loses their place is obviously going to be disappointed and it's a tough call to make. One of the hardest things a political leader has to do," Mr Barnett said.

Senior minister John Day has told the Premier he is sticking around for another term.

Barnett sends message to Nationals

The Premier also sent a message to his junior partner in Government, the Nationals, that he expected them to toe the line on the sale of Fremantle Port.

The party's deputy Mia Davies has warned they will vote against the sale if they were not given enough time to scrutinise the contract.

Mr Barnett did not seem overly concerned by the prospect.

"They can't vote it down by themselves. We will bring it forward as a Government. I would expect the National Party to support it," he said.

Mr Barnett said MPs would have plenty of time to ask questions when legislation to sell the port was debated later this year.