The Australian government has suffered a confidence blow with a key opinion poll finding it is trailing the opposition party for the first time since changing its leader last year.

With an election possible as early as July 2, the Newspoll published on Tuesday found that support for Prime Minister Malcolm Turnbull's conservative coalition was behind the center-left Labor Party 49 percent to 51.

Sydney-based market researcher Newspoll publishes a survey on the major political parties' popularity every two weeks. The survey has become a reputable barometer of Australia's political mood.

When Turnbull challenged his predecessor Tony Abbott for leadership of the government in September, he told reporters: "We have lost 30 Newspolls in a row."

Turnbull on Tuesday refused to comment on the latest Newspoll.