But the CGT and six other unions said they "categorically reject" the request and would march as normal.

"To demonstrate is a constitutional right and it's up to the state to take care of security at demonstrations on the public causeway," they wrote, adding that a stationary protest was "more dangerous" than a march.

"I'm not sure that a union 'fan zone' in the Place de la Nation will be more secure than a (normal) demonstration," said Jean-Claude Mailly, head of the Force Ouvrière union.

Last week, president Francois Hollande threatened to ban all union demonstrations after vandals broke away from one and smashed the windows of a children's hospital, shocking young patients awaiting surgery.

"At a time when France is hosting the Euro (football tournament), when it is faced with terrorism, demonstrations can no longer be authorised if property and people and public property cannot be safeguarded," Mr Hollande's spokesman Stéphane Le Foll told a cabinet meeting.

The marches are against the so-called El Khomri labour reform, named after the labour minister, which would make it easier to hire and fire employees and allow workers to negotiate locally with businesses rather than unions reaching sector-wide deals.

The bill will be put to a vote in the Senate on June 29 before a final vote in the National Assembly on July 5.