No national minimum wage existed prior to 1998, although there were a variety of systems of wage controls focused on specific industries under the Trade Boards Act 1909. The Wages Councils Act 1945 and subsequent acts applied sectoral minimum wages. These were gradually dismantled, until the Trade Union Reform and Employment Rights Act 1993 abolished the 26 final wages councils that had protected around 2,500,000 low-paid workers.
Part of the reason for Labour's minimum wage policy was the decline of trade union membership over recent decades (weakening employees' bargaining power), as well as a recognition that the employees most vulnerable to low pay (especially in service industries) were rarely unionised in the first place. Labour had returned to government in 1997 after eighteen years in opposition, and a minimum wage had been a party policy since as far back as 1986, under the leadership of Neil Kinnock.
The implementation of a minimum wage was opposed by the Conservative Party and supported by the Liberal Democrats.