AUSTRALIAN trade unions urged their members yesterday to canvass for a Labour by-election victory to help bring down the right-wing Liberal government.

The Australian Council of Trade Unions sent out emails calling for members of its constituent organisations to campaign in the Bennelong constituency in the run-up to its December 2 vote.

Liberal incumbent John Alexander quit on Saturday over revelations that he holds British as well as Australian citizenship — disqualifying him from election under a 1901 constitutional rule.

That and seven other resignations has left Prime Minister Malcolm Turnbull’s coalition government without a majority in parliament.

Actu secretary Sally McManus wrote: “If the Liberals lose Bennelong, the Turnbull government could be brought down.

“If they win, with Jacqui Lambie resigning, they will have a greater chance of pushing through laws that will make life harder for working people.”

Independent opposition senator Ms Lambie tearfully announced her resignation yesterday after it emerged that her Scottish-born grandfather did not renounce his British citizenship when he emigrated.

“It is with great regret that I have to inform you that I had been found ineligible by way of dual citizenship,” Ms Lambie told the Senate.

On Monday, independent MP Bob Katter sided with Labour by not referring his opposition colleagues to the High Court — in a bid to win a vote to establish a royal commission probe into the banking sector.

Mr Katter said he hoped George Christensen of junior coalition partner the Liberal National Party would vote with the opposition.

“While they’re electioneering he won’t cross the floor,” Mr Katter said, but “after December 2, it’s game on.”