(Corrects to show Necas government collapsed over scandals)
PRAGUE, Aug 9 (Reuters) - The Czech lower house of parliament will shift a vote on its dissolution for an early election to Aug. 20 from Aug. 16, a party leader said on Friday.
Opinion polls show the Social Democrats are likely to win an early vote by a double-digit margin. They have pledged to undo some of the collapsed centre-right cabinet's pension reform and raise some taxes to replenish public coffers.
The house will most likely agree by a large majority to end its term more than half a year early to overcome political deadlock that has crippled policymaking in the central European country, a European Union member.
On Wednesday, parliament voted against giving confidence to a government formed in June by allies of leftist President Milos Zeman and which was opposed by most political parties.
At the same time, the voting showed no formation could count on a reliable majority to form its own government. That prompted TOP09 conservatives, the second biggest party in the previous centre-right administration, to support an early election plan.
Petr Gazdik, head of the parliamentary caucus of TOP09, said the dissolution vote would be moved from next Friday to Aug. 20 to ensure a quorum of deputies for the motion, which needs 120 votes in the 200-seat lower house.
"Friday is not the most common day for a lower house meeting," he said on Czech Television. "It's not like someone does not want to return from (holidays in) Croatia, but there are several deputies who have serious health or family issues."
Three parties - TOP09, the centre-left Social Democrats and the far-left Communists - have said they would back the plan. They have 122 seats among them. Several other deputies said they would also support the motion.
An early election may be held around October. The Social Democrats are likely to form the next government, although they will probably need a coalition partner. The party speaks in favour of higher taxes for utilities and high wage earners and supports steps to prepare the country for adoption of the euro.
The cabinet of Prime Minister Jiri Rusnok that lost the confidence vote on Wednesday is expected to resign on Friday, or possibly next week. It will stay on in a caretaker capacity, probably until the election.
Rusnok's government replaced the centre-right coalition of Prime Minister Petr Necas that crumbled in June under the weight of a spying and bribery scandal. (Reporting by Jan Lopatka; Editing by Mark Heinrich)