BRATISLAVA, Nov 26 (Reuters) - Slovak lawmakers defied a president's veto on Tuesday to impose a lengthy ban on publishing opinion polls ahead of February elections, a move some opposition parties have cast as an attempt to sideline political newcomers.

Approved by parliament last month, the bill extends the blackout to 50 days from 14 days, third longest in the world after Cameroon and Tunisia according to the Slovak Academy of Sciences.

The measure was adopted ahead of an election due on Feb.

29 next year with the votes of the ruling leftist Smer party, junior coalition Slovak National Party (SNS) and the opposition far-right People's Party-Our Slovakia.

Its authors said the bill aimed to protect voters from disinformation so they could base their decisions on the parties' programmes and actions.

Opposition critics said the measure was a manoeuvre to disadvantage challengers from new parties.

President Zuzana Caputova argued that the bill violates the right to information granted by the Slovak constitution and that it limited political competition.

She said earlier this month she would ask the Constitutional Court to put the implementation of the legislation on hold until a final ruling whether or not it violated the constitution.

The bill does not ban parties from procuring their own opinion polls, as long as they keep the information out of the public domain.

Slovakia, like other countries in Europe, has seen a rise in new parties in recent years.

Caputova, 유로247가입코드 an activist lawyer and political newcomer herself, defeated Smer's candidate in a presidential runoff in March after a late surge in support.

Opposition parties' chances of replacing the three-party government has grown as support for Smer dipped to its lowest level in more than a decade, an opinion poll showed on Tuesday.

Smer has seen a slide in support since last year's murder of an investigative journalist and his fiancee triggered mass protests over corruption and ousted prime minister Robert Fico, who had dominated the euro zone country's politics for a decade.

But his three-party coalition government has survived, led by hand-picked successor Peter Pellegrini, and the socially conservative Smer remains the favourite to take the largest share of the vote.

A coalition of opposition parties, which have ruled out cooperation with Smer, could struggle to present a viable alternative to Smer as it would have to include six or seven parties to win a majority in 150-member parliament.

That might lead to a post-election stalemate, leaving the likely winner Smer without enough partners to form a government and the opposition also short.

* For an interactive graphic, click on website

(Reporting By Tatiana Jancarikova Editing by Mike Collett-White/Mark Heinrich)