Two days after it returned to parliament having lost its majority in an embarrassing byelection defeat, Australia’s government has been dealt another blow with the defection of a Liberal MP.

Julia Banks, an MP from the state of Victoria, resigned from the Liberal party to become an independent, calling out the poor treatment of women in parliament and selfishness of colleagues as she did so.

Her resignation means the coalition government now holds just 74 of 150 seats in parliament.

Julia Banks lashes 'appalling' behaviour against women in parliament Read more

Banks announced that she would become an independent MP at the same time as the prime minister, Scott Morrison, was holding a press conference, suggesting she told few of her colleagues about her plans.

Morrison – previously the socially conservative architect of Australia’s hardline anti-asylum seeker policies – became Australia’s fifth prime minister in just over five years in August after Malcolm Turnbull was ousted in a struggle for power in the Liberal party. In his valedictory speech, Turnbull sounded a warning against the rising tide of populist anti-immigration political rhetoric, promoted from within his own party.

Banks said her “sensible centrist” values remained the same but were no longer matched by the Liberal party, which governs in a coalition with the National party.

“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 parliament.

She said she would decide in the new year about her “future career path”.

In September Banks raised allegations of bullying against women in Australian politics and called for gender quotas in parliament. She also said she would be quitting parliament after the next election.

Timeline Australia - six prime ministers in 10 years (and five in five) Show Hide Kevin Rudd (2007-10) swept to power in a landslide after 11 years of conservative rule under John Howard. Enjoyed immense popularity as the bookish "Kevin from Queensland … here to help", but after he faltered on climate change (having previously described it as “the greatest moral challenge of our generation”), his convictions were questioned and his administration became increasingly erratic. Alienated his colleagues with an at-times abrasive manner, he was ousted by his own deputy …

Julia Gillard (2010-13), Australia’s first (and only) female prime minister, who narrowly won an election after disposing of Rudd, but was forced to govern in minority. She was remarkably productive given the constraints of parliamentary numbers, passing significant legislation on climate change and addressing clerical abuse, but faced misogynistic attacks from the opposition and was undermined from her own side, led by … Kevin Rudd (2013), who assumed the foreign ministry under Gillard, but never put his field marshal’s baton back in his knapsack. He is widely regarded as having led a campaign of leaks against Gillard, destabilising her. Having failed in one tilt to return to the leadership, he succeeded at his second try. However, he had only three months in the job before losing the election to … Tony Abbott (2013-15), who was widely regarded as the best opposition leader in Australia, but an ineffective and inconsistent PM. His term was marked by an adoption of hardline asylum policies, an abandonment of climate change action, and poor economic management. After a series of gaffes and controversial "Captain’s Calls" (including knighting Prince Philip), he was unseated by ... Malcolm Turnbull (2015-18), a former investment banker and lawyer, who was seen as an urbane, articulate, centrist who could appeal to a broad swathe of the Australian population. But he was mistrusted by the conservative wing of his party, and openly derided by some as "Mr Harbourside Mansion", a reference to his grand house on the opposite side of Sydney Harbour to the PM's official residence. But it was Turnbull’s commitment to action on climate change that incensed the climate-sceptic right wing of his party, and he was stalked by his arch-conservative home affairs minister, Peter Dutton. However, Dutton’s attempted coup failed, and the numbers fell 45-40 for the treasurer … Scott Morrison (2018 to date), who as immigration minister had established Australia’s controversial hardline asylum-seeker policies – including indefinite detention on remote foreign islands. The son of a police officer and an active member of a Sydney Pentecostal evangelical megachurch, he voted no in Australia’s plebiscite on same-sex marriage, listed “church” as one of his interests in his Who’s Who report, and regards former prime minister John Howard as his political inspiration. Howard was prime minister for 11 years – a lifetime by today's standards. Ben Doherty

But on Tuesday she said she had been contacted by supporters begging her to stay on as an independent.

Banks is one of five Liberal party women in parliament to have raised bullying allegations. Four of those five have since become independent MPs or left the cabinet.

Banks was vocally dissatisfied with her party when it ousted Turnbull in August. On Tuesday she accused fellow party members of acting for their own power and personal ambition.

In her speech to parliament she said the move against Turnbull had been “led by members of the reactionary right wing … aided by many MPs trading their vote for a leadership change in exchange for their individual promotion, preselection endorsement or silence.”

The removal of Turnbull as leader – which many coalition government members have since sought to distance themselves from – was followed by a disastrous run of events for the government.

Turnbull resigned from parliament and a byelection in his historically safe seat was won by an independent candidate, resulting in the government losing its majority. When Julia Gillard led a minority government before the Labor party lost at the polls in 2013 election, many Liberal MPs said her leadership had been delegitimised.

In another blow, the incumbent Labor government won a crushing victory in the Victorian state election over the weekend.

In his first official week at the head of a minority government, Morrison sought to get back on track with a press conference announcing an early budget and a predicted surplus, but was quickly overshadowed by Banks’ concurrent speech.