Up to 250,000 jobs could be hit if the Government agrees to give new rights to agency worker, the country's biggest business group is warning.
The CBI said it was 'very concerned' that a draft European Union directive will be discussed later this week by EU employment ministers.
A survey of 500 firms showed that up to 250,000 jobs could be jeopardised if agency workers are given the same employment rights as permanent staff.
Deputy director-general John Cridland warned firms could take on fewer agency staff and ask their staff to work overtime instead.
He said: 'Use of temporary agency staff is vital for employers seeking to manage surges in demand. At the same time, these jobs offer quality work to people who actively choose a form of employment that allows them to balance responsibilities or pursue other interests. But this section of the workforce has an uncertain future if the Government caves into pressure for a new EU law.
'Hundreds of thousands of jobs will be put at risk unless Gordon brown rejects it outright.
'As proposed, the directive would seriously undermine the flexibility that temps offer to firms, hurting the economy and making them far more likely to rely on overtime flexibility from existing workers instead.'
Recruitment firm Pertemps said the UK had the edge over its European competitors because of its flexible labour market.
However, Derek Simpson, joint general secretary of Unite, pushed for change. He said: 'Unscrupulous employers are exploiting the scandalous lack of protection given to temporary and agency workers.'