(Bloomberg) -- France’s Constitutional Council rejected a second attempt to hold a referendum on President Emmanuel Macron’s decision to raise the retirement age to 64, as opponents are running out of options to overturn the unpopular pension reform.

The request doesn’t satisfy the necessary conditions, the council said in a ruling published on Wednesday.

The verdict, while widely expected, is a fresh blow for labor organizations and opposition parties. Unions have already called for more strikes on June 6 to maintain pressure on the government with a 14th day of nationwide protests that began in mid-January and still have strong public backing.

The most recent marches on Monday saw the biggest turnout in more than two decades for the Labor Day holiday, which is typically dedicated to workers’ rights. The event saw violent clashes between some protesters and police, however, with hundreds arrested and more than 400 police officers wounded.

The referendum proposal was filed by left-wing opposition lawmakers. It sought to have the current minimum retirement age of 62 enshrined in legislation and would have secured funding for pensions via a higher tax on income.

Had it been deemed constitutionally viable, its proponents would have had nine months to collect the signatures of at least 10% of registered voters, or around 4.8 million people, to move it forward. This likely would have re-invigorated members of the opposition and protesters, though it would still have needed a further six months for possible review by parliament.

This doesn’t completely draw a line under attempts to overturn the reform, as a group of independent, centrist lawmakers, known as LIOT, has submitted a proposal to repeal it that the National Assembly is due to consider on June 8 - two days after the next round of strikes.

The initiative is fraught with challenges, however, as Macron’s party could use delay tactics to prevent its review before a parliamentary deadline of midnight. It’s also unsure whether the conservative Republicains will back the proposal. Even if the National Assembly adopts it, it’s unlikely to get through the Senate.

The referendum procedure hasn’t succeeded since it entered into force in 2015. The council did allow one to proceed over the sale of Paris airports operator Aeroports de Paris, but it failed to garner enough signatures.

The council rejected a first attempt to hold a referendum on the pension reform last month, arguing that it was legally untenable as it wouldn’t have changed the current state of the law. The nine-member body made up chiefly of former politicians and senior civil servants also approved the main elements of the overhaul, allowing Macron to sign it swiftly into law. It’s due to be applied in September.

--With assistance from Tara Patel.

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