By Ioana Patran

BUCHAREST, July 19 (Reuters) - Romania's government has doubled the number of foreign polling stations for a referendum it hopes will impeach the president, officials said on Thursday, after a court ruled that over half the electorate needed to vote for the result to be valid.

The decision, by Prime Minister Victor Ponta's leftist government, saw the number of overseas polling stations increased to 301 from 150 ahead of a national referendum on July 29 that will decide whether President Traian Basescu is impeached for overstepping his powers, something he denies.

Ponta's government joined forces with parliament earlier this month to suspend Basescu, a conservative, and polls show most Romanians will vote to permanently remove him due to his association with austerity measures and a perception of corruption among his political allies.

Romania's political turmoil has raised doubts about its International Monetary Fund-led deal, sending the leu currency to record lows in a country already weathering a recession.

The government initially said it would open a mere 150 overseas polling stations, a move critics said was designed to curb the influence of what has traditionally been an enthusiastically pro-Basescu Diaspora.

But Ponta's government has come under serious pressure from the European Union to respect the rule of law with Brussels sharply criticising the way in which it is handling what amounts to a political power struggle.

The country's Constitutional Court had also weighed in, ruling that more than half the electorate would have to vote for the referendum result to be valid, prompting the government to change tack.

"We have set 301 polling stations," Foreign Minister Andrei Marga told a news briefing. "I congratulate Romanians from the Diaspora for their remarkable civic attitude, that will have consequences and an impact only if they attend the vote en-masse."

Millions of Romanians live abroad, particularly in Spain and Italy which share common language roots with the Latin-based Romanian language, and have traditionally supported Basescu, even tipping the balance in 2009 to ensure his re-election.

Official census data show nearly 1 million Romanians live abroad, though some estimates suggest the number could be as high as 3 million.

Turnout in Romanian elections hovers around the 50 percent level - if Basescu's supporters abstain rather than vote for him, it will be difficult for the government to secure the minimum turnout required.

"Mobilising people to vote is very important for the governing alliance. Because it is very clear that voting intentions show impeaching the president is likely," said Sergiu Miscoiu of the CESPRI political studies think tank. (Writing by Radu Marinas; Editing by Andrew Osborn)