STOCKHOLM, June 15 (Reuters) - Sweden"s government on Tuesday dismissed demands from the Left Party to stop working on a proposal for the abolition of rent controls on new-build properties, setting up a showdown that could topple the centre-left government. The Left party said earlier on Tuesday it would seek support from the main opposition to oust Prime Minister Stefan Lofven if the government did not drop or change plans for market-set rent within 48 hours. The Left Party is not part of the government, but the minority coalition of the Social Democrats and Greens needs its backing to stay in power if the rest of the opposition is united. "Our support will cease to exist if the government implements any proposals for market rents or free rent setting," Left Party leader Nooshi Dadgostar told a news conference. "Stefan Lofven has 48 hours to act." Dadgostar said Lofven could either drop the plans or bring in the Tenants Association to help reshape the planned legislation. However, Morgan Johansson, Minister for Justice, said there was no proposal to withdraw yet but added the government would honour the agreement with its budget partners and eventually put forward the proposal in the autumn. "This is not a game. I would urge all responsible politicians not to make any hasty decisions," he said, adding the country was still facing a pandemic. The Left Party would need the support of at least one other party to force a vote of no-confidence. Only the right-wing, populist Sweden Democrats have indicated they would be willing to join such a move. The Left has said previously that it would not work with the Sweden Democrats, a party with roots in the white-supremacist movement. The main centre-right opposition Moderates and Christian Democrats support easing rent controls. read more Even if a no-confidence vote is held, it is unclear whether Lofven would be ousted. Sweden is due to hold a parliamentary election next year. Forcing the installation of a caretaker government could backfire on opposition parties if voters see potential political chaos as undermining the response to the coronavirus pandemic. The prospect of being forced to vote alongside the Sweden Democrats could also force a last-minute change of heart by the Left Party. A vote of no-confidence would require a majority in the 349-seat parliament to pass.