Attempts to form a new government in Sweden hit the buffers on Monday after Social Democrat leader Magdalena Andersson said she was unable to secure enough support, despite the center-left bloc winning a narrow majority in this month's election.

"I can conclude that there is currently no possibility for me to form a government," Andersson said at a press conference, saying she had lost the support of Sweden's Left Party.

The speaker of Sweden's parliament is now likely to turn to Prime Minister Ulf Kristersson to see if he can form a government. Kristersson's Moderates are the next biggest party after the Social Democrats.

The general election on September 13 saw the center-left opposition winning a narrow majority, taking 176 seats in parliament to the center-right's 173.

The result was driven by a decline in support for the anti-immigration Sweden Democrats in the Nordic nation of 10.6 million people, bucking a Europe-wide trend of gains for the far right.

Despite the center-left's victory, the vote, widely seen as a referendum on Kristersson's promise to bring the far-right Sweden Democrats into a ruling coalition, has left forming a stable government fraught with difficulties.

Andersson said she had given up trying to form a government after the Left Party, one of the parties she needed to form a majority, said it would support a candidate from the center-right as speaker of parliament. 

The Left Party has said previously it will only support Andersson as prime minister, while the liberal Center Party has said it will oppose a government that includes cabinet posts for the Left Party.

Andersson would likely get another shot at trying to form a government if any center-right attempt fails.

Kristersson formed a right-wing coalition in 2022 by aligning his center-right Moderates with the Loberals and Christian Democrats, while also relying on the far-right Sweden Democrats for cruical support in parliament. 

In the run-up to the 2026 election, Kristersson said that if victorious he would give Sweden Democrats politicians key ministerial positions, ending the country's historical governmental cordon sanitaire against the far right. However, for the first general election since its inception in 1988, Sweden Democrats gathered fewer votes, a smaller share and fewer seats. 

The speaker can put four candidates forward to parliament for approval, but if each is rejected, Sweden will hold a new election.

Casting a further cloud over the process, police said on Friday they had started preliminary investigations into five complaints of election fraud around Stockholm.

The probes come days after prosecutors opened a separate investigation into suspected fraud in the central Swedish town of Borlange, a case that could put 11 parliamentary seats in play if the Election Review Board orders a re-run of the vote there.

In 2018, Social Democrat Stefan Lofven took 134 days to form a new government.