Sweden's Magdalena Andersson resigns hours after appointment as first female PM

"There is a constitutional practice that a coalition government should resign when one party quits," Andersson, a Social Democrat, told reporters.

"I don't want to lead a government whose legitimacy will be questioned."

Andersson said she hoped to be elected to the position again soon as the head of a minority government made up of only the Social Democrats.

In a turbulent sequence of events, Andersson became the first woman elected to the post of prime minister in Sweden after clinching a last-minute deal with the Left Party to raise pensions in exchange for its backing in Wednesday's vote.

But the small Centre Party then withdrew its support for Andersson's budget, because of the concessions made to the Left, leaving her budget with insufficient votes to pass in parliament.

Parliament instead adopted an alternative budget presented by the opposition conservative Moderates, Christian Democrats and far-right Sweden Democrats.

The fatal blow came when Greens leader Per Bolund said his party could not tolerate the opposition's "historic budget, drafted for the first time with the far-right", and quit the government.

Among other things, it said the opposition's planned tax cut on petrol would lead to higher emissions.

Speaker of Parliament Andreas Norlen said he had accepted Andersson's resignation and would contact party leaders before deciding Thursday how to proceed.

(AFP)