Business leaders have sounded a final plea for the European Parliament to keep the UK's opt-out from the Working Time Directive in Wednesday's vote.
Both business body the CBI and manufacturers' organisation the EEF insisted it was important for UK employees to have the opportunity to work more than an average 48 hours per week.
MEPs will vote in Strasbourg on Wednesday on amendments to the Working Time Directive, one of which would see the UK's cherished opt-out scrapped.
John Cridland, deputy director-general at the CBI, said: "This move would affect workers across all sectors of our economy who currently choose longer hours, from accountants to medical researchers.
"The ban on longer hours could create particular problems in tough economic conditions. Workers in a company fighting for survival who wanted to go the extra mile could be stopped from doing so. People who want to work longer hours to help support their family in hard times could also be denied this right."
Meanwhile, David Yeandle, head of employment policy at the EEF, stepped up his efforts to convince MEPs to vote in favour of the UK retaining its opt-out.
He wrote to UK MEPs expressing his views, while the EEF's sister organisations across Europe wrote similar missives to their MEPs.
Yeandle attached copies of letters to the rapporteur and shadow rapporteur from the chairman of CEEMET, the European employers' organisation to which EEF belongs, calling for the opt-out to be retained.
The European Council agreed in June this year that the UK would keep its opt-out, after it agreed to the deal on agency workers, which allows temps the same rights as permanent staff after just 12 weeks in a job.
But since then, the social affairs and employment committee at the European Parliament has voted to amend this agreement, and scrap the opt-out.
If MEPs vote on Wednesday to end the opt-out there will be an eight-week conciliation period while the new wording is worked out. So the picture may not be clear until March.
The directive will not have to be transposed into UK law for three years from the date of the directive's official publication, so it is unlikely to affect employers until 2012.
Last week, Li