Draft European Union (EU) laws obliging firms to give temporary staff the same rights as full-time workers could destroy thousands of jobs, a leading business group has warned.
The CBI said the proposals, if implemented in their current form, would deter many employers from taking on temporary workers, triggering a cut in job opportunities.
"If the EU is serious about economic reform it should not be trying to drag the UK's flexible and successful labour market in the direction of other countries where they have high unemployment," said CBI director general Digby Jones.
According to a CBI survey carried out with employment agency Pertemps, 47% of employers would take on fewer temporary workers if the law were adopted.
The UK is thought to have the highest number of temporary workers in Europe.
The CBI's warning came as EU employment ministers prepared to discuss the proposals at a meeting in Luxembourg on Tuesday.
The proposals would oblige firms to give temporary workers the same pay and conditions as full-time staff after six weeks' employment.
At present, temporary staff in the UK are not entitled to the same range of pay and holiday benefits as their full-time counterparts.
The CBI says equal pay and conditions should be introduced only after a full year's employment.
But trade union groups dismissed the CBI's claims, and welcomed the proposals as an opportunity to end the UK's "two-tier" employment system.
"There is absolutely no factual evidence for the claim that extending these rights to agency temps will cost jobs," said Brendan Barber, general secretary of the TUC.
At Tuesday's ministerial meeting, the UK government is expected to argue in favour of a one-year delay before extending full-time rights to temporary workers.