PARIS, June 10 (Reuters) - The far-right National Rally was forecast on Monday to win a snap election in France but fall short of an absolute majority in the first opinion poll published after President Emmanuel Macron's shock decision to dissolve parliament.

Following a massive loss for his Renaissance party in Sunday's European Parliament election, Macron announced snap elections for the lower house of parliament, with the first round scheduled for June 30, less than three weeks away, and the run-off on July 7.

Marine Le Pen's anti-immigration, eurosceptic National Rally party, known as RN, would win 235 to 265 seats in the National Assembly, a huge jump from its current 88 but short of the 289 needed for an absolute majority, according to the survey by Toluna Harris Interactive for Challenges, M6 and RTL.

Macron's centrist alliance would see its number of lawmakers possibly halve, from 250 to 125-155, the poll showed on Monday. Leftwing parties could together control 115 to 145 seats, though each party could run on its own.

There is no certainty the RN would run the government, with or without an alliance with others. Other scenarios include a wide-ranging coalition of mainstream parties, or a completely hung parliament.

But Macron's shock decision does offer the increasingly popular far right a real shot at power. Amounting to a roll of the dice on his political future, this immediately sent the euro down, while French stocks and government bonds tumbled. RN won 31.4% of the European Parliament vote while the Renaissance party coalition had 14.6%.

Even if RN does score a majority in the French parliament, Macron would remain president for three more years and still be in charge of defence and foreign policy.

But he would lose control over the domestic agenda including economic policy, security, immigration and finances, which would in turn impact other policies, such as aid to Ukraine, as he would need parliament's backing to finance any support as part of France's budget.

"We're still in shock," Emmanuel Pellerin, a lawmaker from Macron's Renaissance party, told Reuters. "Everything points to the RN winning a relative or absolute majority. But that forces the French to think about what is at stake."

In that context, political parties were racing to field candidates and discuss possible alliances.

Photo from Reuters