* French polls open on Sunday at 8 a.m.

* Macron needs 289 seats for absolute majority in parliament

* Pollsters say he may fall short as smaller parties make gains

By Ingrid Melander

PARIS, June 19 (Reuters) - France votes on Sunday in a high-stakes parliamentary election that could deprive centrist President Emmanuel Macron of the absolute majority he needs to govern with a free hand.

Voting starts at 8 a.m. (0600 GMT), with initial projections expected at 8 p.m. (1800 GMT) in an election that could change the face of French politics.

Pollsters predict Macron's camp will end up with the biggest number of seats, but say it is in no way guaranteed to reach the 289 threshold for an absolute majority.

Opinion polls also see the far right likely to score its biggest parliamentary success in decades, while a broad left-green alliance could become the largest opposition group and the conservatives find themselves as kingmakers.

If Macron's camp does fall short of an outright majority, that would open a period of uncertainty that could be solved by a degree of power-sharing among parties unheard of in France over the past decades - or result in protracted paralysis and repeat parliamentary elections down the line.

Macron, who wants to push up the retirement age, pursue his pro-business agenda and further European Union integration, won a second term in April.

After electing a president, French voters have traditionally used legislative polls that follow a few weeks later to hand him a comfortable parliamentary majority - with Francois Mitterand in 1988 a rare exception.

Macron and his allies could still achieve that.

But the rejuvenated left is putting up a tough challenge, as rampant inflation that drives up the cost of living sends shockwaves through the French political landscape.

If Macron and his allies miss an absolute majority by just a few seats, they may be tempted to poach MPs from the centre-right or conservatives, officials in those parties said.

If they miss it by a wider margin, they could either seek an alliance with the conservatives or run a minority government that will have to negotiate laws on a case-by-case basis with other parties.

Even if Macron's camp does win the 289 seats or more it needs to avoid sharing power, it is likely to be thanks to his former prime minister Edouard Philippe, who will be demanding more of a say on what the government does.

So after five years of undisputed control, Macron, known for his top-down approach to power, is looking at a new mandate where he will need to strike more compromises.