Equal rights for agency staff have been called for by the Trades Union Congress (TUC).
The TUC is calling on the government to ensure agency workers are treated fairly by bringing in new regulations as employers can currently pay directly employed staff more for the same work.
TUC general secretary Brendan Barber commented that some people choose agency work as a preferred method of employment.
"Some people, including women and older workers, are always going to prefer to work a series of temporary contracts, but just because they opt for agency work shouldn't mean they are treated less fairly at work," he said.
Mr Barber noted that agency workers are also given fewer holidays by employers and no contractual sick pay.
The TUC is calling for the government to encourage other EU members to sign up to the EU Temporary Agency Directive in a bid to protect the rights of temporary workers.
Mr Barber recently commented on gender pay gap statistics from the Office for National Statistics, calling the slow progress of the gap between male and female salaries as "completely unacceptable".