Businesses that close plants deemed to be still economically viable face fines under a new law adopted by the French parliament on Monday.

The so-called "Florange Law" was named after an ArcelorMittal steelworks in the north eastern French town where the plant's imminent closure became a symbol of Francois Hollande's 2012 presidential campaign.

It obliges the head of any enterprise with more than 1,000 employees who wants to close down a plant to spend three months looking for a buyer first.

Failure to do so will result in a fine amounting to €28,000 per job lost, up to a limit of 2 percent of annual revenue.

The Florange plant did eventually close, but the law fulfils a promise President Hollande made in a speech to its workers at the time.

It has attracted criticism from both sides of the fierce debate over industrial policy in the country. Employers' groups say the law contradicts Hollande's pledge to be more business friendly, while trade unions say it does not go far enough to protect French workers.