Unions have condemned a European Commission plan to shelve a draft directive granting temporary staff the same rights a permanent workers.
Temporary workers have fewer rights than permanent staff
The draft Agency Workers Directive (AWD) would have ensured that temporary workers enjoying the same conditions as permanent staff.
The AWD is one of 68 draft directives earmarked by the European Commission for shelving in a bid to cut red tape.
But the TUC said the Commission's move was a "major setback for temps."
"For four years the agency workers directive has been blocked by various governments, including our own, and now it is destined to sit on a Brussels shelf for many more years to come," Brendan Barber, TUC general secretary said.
"Agency workers deserve a better deal...Today's announcement gives a green light to those unscrupulous employers who will continue to exploit agency workers."
But Gareth Osborne, managing director of the Recruitment & Employment Confederation, rebutted claims that temps are exploited.
"Temporary workers are sick of being patronised and portrayed as systematically undervalued and underpaid. The first hand accounts we have confirms that flexible working is increasingly valued," he said.
The Commission's imitative to cull 68 draft directives is being strongly backed by the UK government, which currently holds the EU presidency.
But the President of the European Parliament, Josep Borrell, said the parliament would consult lawyers to check whether the Commission had the power to withdraw all 68 pieces of legislation on its hit list.
He said it was unclear that they had the legal right to scrap proposals that member states had already discussed, and taken a common position on.
However, enhanced rights for temps may not disappear altogether from the EU agenda.
The Commission said it "reserved the right to reconsider the proposal (greater rights for temp workers) in light of future discussions."
Under UK law, temporary workers have no right to redundancy pay, to claim unfair dismissal or to take maternity leave.
Unions also claim that temps often have great difficulty claiming sickness and holiday pay.
The UK is one of three EU countries where temps are paid less than staff for the same work, the TUC has claimed.
But the plans to grant temporary workers the same rights as permanent staff has been opposed by UK business on the grounds that it has the potential to push up costs and harm competitiveness.
Recently, the Confederation of British Industry (CBI) said that the UK had a successful labour market which would only be jeopardised by extra regulation such as the AWD.