* Police say 30,000 took part in Paris march
* Fierce opposition on hard left to labour reforms
* PM Ayrault says government measures will bear fruit slowly
By Muriel Boselli
PARIS, May 5 (Reuters) - Ten of thousands of far-left French protesters marched to denounce economic austerity on Sunday to mark the end of President Francois Hollande's first year in office.
The march, organised by the Left Front coalition, drew a range of left-wingers from greens to trade unionists to the symbolic venue of Bastille Square, site of a Paris prison that was stormed during the French Revolution of 1789.
Turnout was estimated by organisers at 180,000 but by police at just 30,000. Although not massive, it highlighted fierce opposition on the left to the Socialist president's market-friendly reforms, such as corporate tax breaks and the loosening of labour rules to make hiring and firing slightly easier.
With France on the edge of recession, unemployment at an all-time high and euro zone partners pressing him to cut the budget deficit, Hollande has suffered the sharpest fall in popularity of any president in more than half a century.
Wearing his signature red scarf, Jean-Luc Melenchon, a fiery leftist orator and former presidential candidate, castigated what he called the government's broken promises. Protesters roared back with chants of "Resistance!"
"We don't want the financial world taking the power, we don't accept austerity measures which destine our people, like all people in Europe, to never-ending pain," Melenchon told the crowd.
While the protest gathered a large swathe of left-wing sympathisers, Hollande still has the strong backing of centre-left lawmakers and the moderate CFDT trade union group, which backed the labour reform and did not join the march.
Responding to the marchers, Prime Minister Jean-Marc Ayrault told TV channel TF1: "There is no austerity, that's a propaganda invention."
But he added: "I understand their impatience and it's why we need to battle. We've sown seeds but they will need time to bear fruit because the land had been abandoned a long time. Our reforms are geared towards growth and investment, not just austerity. They will bear fruit little by little."
Ayrault added the government was considering cutting its stake in some part state-owned companies to finance investments.
In a move hailed as a victory by Finance Minister Pierre Moscovici, the European Commission on Friday gave France two more years until 2015 to bring its budget deficit below the EU ceiling of 3 percent of gross domestic product, from 4.8 percent last year. The government says it will hit the target by mid-2014.
But Melenchon was dismissive. "Stop the lies. It's not two years of respite the European Commission is giving us but two years of blackmail," he said.