Portugal could face its third early parliamentary election in just over three years after Prime Minister Luis Montenegro proposed a confidence motion in his centre-right minority government.

Portuguese Prime Minister Luis Montenegro said he plans to seek a confidence vote in a parliament where he only has minority backing, after struggling to put an end to speculation about potential conflicts of interest related to a company owned by his family.

Portugal's cabinet has decided to go ahead with a motion of confidence in the centre-right government that is opposed by the main opposition parties, it said on Thursday, with a parliamentary vote expected to take place next Tuesday.