(Refiles to fix typo in headline, add missing word in last paragraph)
STOCKHOLM, Sept 28 (Reuters) - Swedish Social Democrat leader Magdalena Andersson said on Monday she would tell the speaker of parliament that she was unable to form a government in the current situation, after an election earlier this month gave her centre-left bloc a narrow majority.
Her decision came after the Left Party said over the weekend it would back a candidate for parliament speaker from the rival Moderate Party, which Andersson said undercut her attempt to build a government.
"Of course, I take the Left Party's message seriously, and based on that and the conversations I have had, I can conclude that there is currently no possibility for me to form a government," she told a press conference.
The centre-left won 176 seats to 173 seats for the incumbent right bloc in a vote widely seen as a referendum on Prime Minister Ulf Kristersson's promise to form a coalition with the far-right Sweden Democrats.
The speaker will now decide to whom to hand the task to seek to secure backing for a government, potentially Kristersson.
(Reporting by Simon Johnson, writing by Stine Jacobsen, editing by Louise Rasmussen)
