Your contract of employment will contain an express term specifying your rate of pay, which is a matter of agreement between you and your employer. In accepting the contract of work, you also accept the offered pay rate.
As well as paying at least the National Minimum Wage rate, employers must make sure they comply with anti-discrimination law. For example, equal pay legislation bans unjustified salary differences between men and women doing the same job, or work of equal value.
Pay rates for agency workers on short-term hires (less than 12 weeks) are usually negotiated between the employer and the agency concerned, although some collective agreements negotiated by unions will cover this issue.
There is no law against paying more to agency workers than to equivalent permanent staff.
A higher hourly and daily rate for agency staff may reflect in part the fact that these workers are only paid for when they work and do not have access to some of the occupational benefits that a firm's core workforce may enjoy. Although some agency workers now benefit from equal treatment rights under the Agency Workers Regulations 2010, the right to equal treatment only covers pay, holiday, working time and some pregnancy rights. Sick pay, redundancy pay, occupational pensions and maternity pay rights are specifically excluded.