French unions strike over Nicolas Sarkozy's pension plans Reuters

French protesters furious over the government's proposals to change the pensions system flooded the boulevards of cities from Paris to Marseille today as Nicolas Sarkozy's embattled labour minister presented the reform to a parliament echoing with jeers.

Huge numbers of people – 1.1 million according to the government, 2.7 million according to the leading CGT union – turned out throughout France to demonstrate against plans to raise the retirement age from 60 to 62. There was significant disruption caused to trains, planes and public services as a result of the strike. In the capital alone, the CGT union estimated the number of protesters at 270,000.

"It is about time the government reacts," said Francois Chérèque, leader of the CFDT union, last night, claiming the "massive" turnout had given the protesters moral authority to demand changes to the bill.

In the Assemblée nationale, Eric Woerth, the minister seriously undermined by the scandal surrounding L'Oréal heiress Liliane Bettencourt, hailed the reform as one of "courage and … reason". Fighting to make himself heard above booing from the opposition, he said the proposals were "an essential element of our social pact".

For its opponents, however, the law is an affront to France's traditions of worker rights and generous post-career provision. "The legal [retirement] age of 60 years old is … a question of justice," said Martine Aubry, leader of the Socialist party. She has said she would reinstate the sacrosanct Mitterrand-era retirement age if elected in 2012. "Higher life expectancy has to be taken into account, but not like this," she told Le Parisien.

Pointing to demographic and economic necessity, the government wants to trim the country's budget deficit and avoid a pensions black hole in years to come. France has one of the lowest retirement ages and most generous retirement package of any European country; it also has a £27bn deficit in its state pension fund which could more than double by 2030.

To combat this, the law proposes raising the legal age of retirement to 62 by 2018, raising the age of full pension entitlement from 65 to 67, and extending the period of contributions, employer and employee, from 40.5 years to 41.5 years by 2020.

Sarkozy, whose approval ratings are consistently in the mid-thirties, regards the reform as crucial for France's future financial health, while observers say its passing is crucial to his re-election.

But, after today's turnout, the unions and leftwing opposition will be pushing for concessions. They say that more can be done to ease the burden on people who, for instance, started work in their teens, people – often women – with several different pensions because of disjointed careers, or those toiling in dangerous or strenuous industries.

One employee at a PSA Peugeot Citroen car factory in eastern France told Le Monde his job was exhausting. "I have colleagues who have been here for 40 years. The very idea that they will be made to work two more years makes me mad," he said. "Pushing people to the limit will lead to a greater occurrence of workplace illness, which will serve merely to deepen the hole in the state health service. Where's the logic in that?"

While adamant that there will be no rowing back on the main pillars of the reform, Sarkozy has indicated he is willing to consider tweaking the proposals to placate the unions. Today, in the Assemblée nationale, the opposition drew on the action on the streets to demand the government give in. "Are you going to hear the anger of the people?" asked Lionel Paul, a Communist MP, before members of his party prompted a temporary suspension of parliament by dumping their pension petitions on the desk in front of Francois Fillon, the prime minister.

In remarks to MPs, Fillon goaded the Socialist opposition for having failed to act on the issue while in power and defended the government's "reasonable" choice which, he said, was "indispensable for the financing of French people's pensions".

The latest opinion polls show around two-thirds of French people support today's strike, although opinions are more divided over whether the retirement age should be kept at 60.

Roland Cayrol, a political academic at Sciences Po in Paris, believes the big turnout was about more than just opposition to the pensions changes, to which, he said, many French people had become "resigned". What had brought many onto the streets, he said, was a "big moment of social exasperation. Never in the history of opinion polls have French people been so convinced of social injustice," he said.