The principal legislation governing sexual orientation discrimination from 1 October 2010 is the Equality Act 2010. The Act represents the most significant overhaul of the legislation covering discrimination since the 1970s.
Before 1 October 2010 the key legislation was the Employment Equality (Sexual Orientation) Regulations 2003 (SI 2003/1661) (the Regulations). These Regulations had been in force since 1 December 2003 implementing the sexual orientation aspects of EC General Framework Directive (2000/78).
There is a helpful and detailed Code of practice on employment and other non-statutory guidance available on the Equality and Human Rights Commission (EHRC) website.