In the run-up to May 21 federal elections, with the government trailing in opinion polls, Defence Minister Peter Dutton has been warning voters not to trust the opposition Labor Party with Australia's security.

Dutton called a news conference in Perth to say that a Chinese surveillance vessel had been sailing close to the West Australian coastline for the "last week or so".

The minister said he could not reveal when Australia became aware of the ship for "operational reasons". But a defence ministry media statement showed it had been tracked from May 6-13.

Australia's air force was monitoring the ship, which had entered the country's exclusive economic zone, he said.

The zone extends beyond Australia's territorial waters and the government has previously said it accepts Chinese spy ships can operate there.

"Its intention, of course, is to collect intelligence right along the coastline, and it has been in close proximity to military and intelligence installations," Dutton said.

The defence minister said it was "unusual" in the way that it had sailed so far south and was hugging the coastline.

- PM says he can change -

"I think that it is an aggressive act and I think particularly because it has come so far south," Dutton said.

The defence minister provided a map of the ship's route and video of the surveillance vessel identified as the Haiwangxing -- a Dongdiao-class auxiliary intelligence ship.

Dutton said he was speaking about the spy ship "because it is best to be honest and open with the Australian public".

But he took the opportunity to warn voters not to support opposition Labor Party leader Anthony Albanese: "It is a huge risk of this election not to go to Mr Albanese because they just don't take defence seriously."

Last November, a Chinese spy ship was spotted off the coast of Darwin within Australia's exclusive economic zone.

"They can be in those areas, just like we can be in the South China Sea. And so, we don't make an argument about that," Prime Minister Scott Morrison said at the time.

As he battles to close the opinion poll gap with Labor, Morrison promised Friday that he could change his own behaviour if re-elected.

The prime minister said he had been "a bit of a bulldozer" to get things done during the pandemic.

"As we go into this next period on the other side of this election, I know there are thing that are going to have to change with the way I do things, because we are moving into a different time," Morrison said.