The act extends essentially to England and Wales, but some provisions (for example, relating to modern slavery statements and cross-border pursuit) apply in Scotland and Northern Ireland.

The bill was introduced to the House of Commons in draft form in October 2013 by James Brokenshire, Parliamentary Under Secretary for Crime and Security.

[5][6][7] The draft bill included no measures to counter the use of slave labour abroad as the Home Office believed that asking businesses to audit and report on modern slavery in their supply chains would be an "additional burden".

There are, however, no legally binding requirements to conduct due diligence on supply chains and there are no criminal or financial penalties for non-compliance.

At the point of launch, on 1 April 2016, it was partnered with, amongst others, the Welsh Government, the Chartered Institute of Procurement & Supply, the International Chamber of Commerce (ICC), and Business West.

[12] In 2019 the UK Government committed to publishing a Modern Slavery Statement of its own, reflecting the requirements imposed on larger businesses under section 54 of the 2015 Act.

[13] In November 2014 Fiona Mactaggart MP added an amendment to the bill concerning prostitution, aimed at criminalising the purchase of sex.

McDonnell quoted Reverend Andrew Dotchin, a founding member of the Safety First Coalition: "I strongly oppose clauses on prostitution in the Modern Slavery Bill, which would make the purchase of sex illegal.

[20] Parosha Chandran, a human rights barrister and United Nations expert on trafficking, claimed that "the bill is very poor on victim protection".

[26] In January 2024 a select committee of the House of Lords was appointed to consider the Act's implementation, impact, effectiveness, how it has been affected by subsequent political developments and whether it requires improvement.

It noted that the fragmentation of the labour market had made preventing modern slavery more difficult, and proposed the creation of a specialist enforcement body.