Support for the two parties backing Greece's technocrat Prime Minister Lucas Papademos remains low as leftwing, anti-bailout parties gain ahead of elections expected in late April or early May, a poll showed on Thursday.

Support for the conservative New Democracy party stood at 23 percent, while the socialist PASOK party's ratings stood at 13.5 percent, according to a survey by pollster Pulse RC.

Backing for the smaller, anti-bailout parties remained high -- with the KKE communists and the Left Coalition taking 12.5 percent each, followed by the Democratic Left with 10.5 percent.

Based on current poll numbers, New Democracy would fail to win an absolute majority and would have to depend on its current co-ruling partner -- the Socialists -- to govern.

The two parties have been suffering in polls because of their support for debt-laden Greece's second bailout package that imposes painful austerity cuts on Greeks.

The next election is expected to be called once the Greek parliament passes a law on the new bailout this month, with officials predicting it will be held in late April or early May.

The survey was carried out on March 12-13, after Greece concluded a successful bond swap. But 31 percent of Greeks said the swap was negative for Greece, while 36 percent said it did not change the current situation and only 26 percent said it was positive for the country.

(Reporting by Lila Chotzoglou; Edited by Richard Meares)