STOCKHOLM • Sweden's first female prime minister, Ms Magdalena Andersson, got the worst possible start to her tenure when she was forced to resign only hours after her historic appointment.

The resignation was triggered after a junior partner to Ms Andersson's Social Democrats left her government on Wednesday over the loss of next year's budget vote.

The 54-year-old former finance minister, who had to step down to get another go at securing the top seat, said she is still ready to lead a one-party Cabinet and was set to face a new vote as early as yesterday. "I have asked the Speaker to be relieved of my duties as prime minister," Ms Andersson told a news conference. "I am ready to be prime minister in a single-party, Social Democrat government."

The latest turbulence shows how the rise of the anti-immigrant Sweden Democrats has made it extremely difficult to form viable coalitions. Long seen as a two-horse race between a relatively unified centre-right and a bloc of left-leaning parties led by the Social Democrats, the country's political landscape has been upended by the nationalists, whose popularity is fed by worsening gun crime and tensions over immigration.

"I understand that this may look very messy, and what has happened is completely unique," Ms Andersson said as she announced her resignation less than eight hours after being appointed. "Despite the fact that the parliamentary positions appear unchanged, the issue should be tried anew. I don't want to lead a government whose legitimacy might be questioned."

The government briefly collapsed once already this year because of opposition to a plan to ease rent controls on new apartments.

Ms Andersson's predecessor Stefan Lofven quit in June before being reinstated, and then made a surprise resignation in August. The former union leader, a figure who was able to cobble together impossible alliances, had banked on cooperating with the centre-right to keep the Sweden Democrats out of power.

Now, with an election less than 10 months away, the rising political instability may help the nationalists get a shot at power.

Still, current opinion polls indicate no clear winner.

While the junior partner, the Green Party, said it won't be part of Ms Andersson's Cabinet, it said it would not block her appointment. That means she will probably get voted in again even if governing will be incredibly difficult with elections due in September.

A centre-right party that has previously supported the government refused to back Ms Andersson's budget in a parliamentary vote earlier on Wednesday, sealing the fate of the government's Bill in favour of a competing proposal by conservative parties.

The amendment means some of the government's key reforms, such as an extra week off for families, are ditched in favour of more spending on the justice system and a gasoline tax cut.

The fact that it has taken this long for Sweden to get a woman prime minister is embarrassing for many in a country that introduced universal suffrage 100 years ago and has long championed gender equality.

Neighbouring Norway got its first woman leader 40 years ago.

BLOOMBERG