Banks, the 56-year-old member for the Chisholm, cited the leadership coup against former prime minister Malcolm Turnbull as her main reason for defecting and becoming an independent.

“The Liberal Party has changed, largely due to the actions of the reactionary and regressive right wing who talk about and to themselves rather than listening to the people,” she told the lower house today.

“Effective immediately, I will serve as a member of this House of Representatives as an independent representative.”

Banks pointed the finger at the “reactionary right wing” of the party for toppling her favoured leaders, Turnbull and former deputy leader Julie Bishop.

“Both visionary, inspiring leaders of sensible, centrist Liberal values with integrity and intellect,” she said.

“And with significant support from my local community and across Australia as leaders of our nation.”

The newly independent MP said her former colleagues had been driven by their individual self-interest rather than working for the good of the Australian public.

“The coup was aided by many MPs trading their vote for a leadership change in exchange for their individual promotion, pre-selection endorsements or silence.”

Banks gave the government the assurance of confidence and supply, adding she would make a decision about her political future in the new year.

The coalition government had already slipped into a minority yesterday, after Wentworth MP Kerryn Phelps was sworn into parliament to replace Turnbull.

Meanwhile, the federal government today announced it will bring the budget forward by a month to allow for an election in May.

Prime Minister Scott Morrison says the April 2 budget papers will finally show a surplus.

The size of the surplus will be clearer when the government’s mid-year budget review is published on December 17.

Asked about the prospect of a May election, Morrison told reporters: “You do the maths … to have a half-Senate and House of Representatives election, that would have to be conducted by the 18th of May.”

“It is absolutely our intention to have the budget before the election and to deliver a surplus budget, a surplus budget that we promised to deliver.”

Treasurer Josh Frydenberg said the budget statements will distinguish between the coalition and Labor as Australians head to the polls.

“The next election will be a stark contrast,” he said.

“A contrast between a coalition government that is growing the economy and has an economic plan that is working and is for the future, and the Labor Party, who wrongly believe you can tax yourself to prosperity.”

But the treasurer also stressed a strong economy was a means to an end, rather than an end in itself.

“The benefit of a strong economy is that you can provide the essential services – the defence, the border security, the infrastructure, the disability support,” Frydenberg said. “The things that Australians need and deserve.”

Neither Morrison mor Frydenberg was worried shifting commodity prices could cause hiccups in their budget planning, because Treasury’s commodity forecasts were “very conservative”.

-AAP