LISBON, Jan 16 (Reuters) - Portugal"s ruling Socialists extended their lead in a new poll on Sunday, two weeks before a snap election, widening the gap between them and the main opposition party, the Social Democrats. The survey, carried out by pollsters Aximage for newspapers Jornal de Noticias, Diario de Noticias and radio station TSF, gave the current premier Antonio Costa"s PS party a 38.1% share of the vote, up from 35.4% last month. It still leaves PS short of a majority, which under the proportional representation system, equates to between 42% and 45% of the vote. The poll put the Social Democrats (PSD), led by Rui Rio, at 28.5%, down from 33.2% in December. PS and PSD are now separated by around 10 percentage points, according to the survey. In October, Costa"s two former allies - the Communists and the Left Bloc - sided with right-wing parties to reject the minority government"s budget bill, triggering the snap election set for Jan.30. If PS fails to win a majority they will need the support of one or more parties to pass legislation. The Left Bloc and the Communists saw support at 7.4% and 4.8% respectively in the Aximage poll. In a debate last week, Costa said an alliance between the three was no longer possible but signalled he might seek support from the People-Animals-Nature party. Aximage"s poll gave them 2.1% of the vote. Analysts say the election alone might not solve the political impasse as no party or workable alliance is likely to achieve a stable majority. According to the poll, which surveyed 807 people on Jan. 6 to Jan. 12 with a margin of error of 3.45%, far-right party Chega would become the country"s third largest party, polling at 9%, up from 6.2% in December.