The TUC has been accused of putting jobs at risk after coming under attack from employers and recruitment firms for suggesting that agency workers are being denied equal pay because the Government has failed to put European rules into practice.
The union organisation has lodged a formal complaint to the European Commission about the issue, claiming that agency staff are being paid less than full-time employees in the same job.
Katja Hall, the CBI's chief policy director, said: "The TUC appears to have conveniently forgotten that it signed up to the Swedish derogation as part of the deal that brought in the Agency Workers Directive.
"While businesses find the directive a nightmare to administer, the final deal carefully balanced the needs of businesses and employees - and the Swedish derogation is a key part.
"Many firms prefer to pay an agency to provide temps using the Swedish derogation rather than face the bureaucracy involved with complying with the directive. This is perfectly understandable and entirely within EU law."
Kate Shoesmith, head of policy at the Recruitment and Employment Confederation, said the TUC was being "misleading", adding: " Most workers are now much better off as a result of the agency workers regulations as they receive equal pay after 12 weeks.
"Or they can sign up to become a permanent employee of their recruitment agency where they are paid when not on assignments and have access to benefits that they would not have been eligible to before such as protection from unfair dismissal, maternity leave and statutory redundancy pay by signing a pay between assignments contract.
"The UK economy has made a positive start on the long road to recovery and to disrupt this excellent progress by picking at regulations that the unions played a key role in constructing could put workers' jobs at risk."
TUC general secretary Frances O'Grady said: "The recent agency worker regulations have improved working conditions for many agency workers without causing job losses. However, the regulations are being undermined by a growing number of employers who are putting staff on contracts that deny them equal pay."