PARIS (Reuters) - Some 64 percent of French voters would approve the European Union's new pact on fiscal discipline if it was put to a referendum, a poll showed on Monday ahead of its planned ratification.

President Francois Hollande's Socialist government will submit the pact to the lower house of parliament on Tuesday.

With the conservative opposition backing the pact, it is expected to be approved in a vote around October 9 despite the opposition of a vocal minority of Socialist legislators and their far-left and Green allies.

Thousands of protestors marched through Paris on Sunday in protest at the pact, which holds governments to deficit targets that in France would require more cuts, in the first major display of public anger to face Hollande since his election in May.

With unemployment already at a 13-year high, many French are hostile to the prospect of more austerity.

Still, Monday's survey by pollster BVA and published by Le Parisien newspaper showed that 54 percent of those respondents who had voted for Hollande in May approved of the fiscal pact.

Some 75 percent of supporters of conservative former president Nicolas Sarkozy would back it in a vote according to the poll of 991 people carried out on September 27-28.

The treaty's central aim of restricting governments' structural deficits to within 0.5 percent of GDP in the medium-term won approval from 72 percent of people polled.

France's Constitutional Court has ruled that the pact, which was agreed in March by Sarkozy and 24 other European leaders, does not require a change to the constitution, allowing Hollande to skip a referendum and avoid a bi-cameral parliament vote.

In an effort to cut the public deficit to 3 percent of GDP, from a forecast 4.5 percent this year, the government last week unveiled 20 billion euros in tax rises and a further 10 billion in spending cuts in the country's toughest budget in 30 years.

(Reporting By Daniel Flynn; Editing by Catherine Bremer and Patrick Graham)