Ministers must act “quickly and effectively” to ensure thousands of victims of modern slavery in the UK are protected, a report has said.
A review of the Modern Slavery Act said laws must be strengthened and it makes 80 recommendations.
Laws introduced in 2015 included tougher sentences and more help for people forced into labouring, domestic servitude, sex work and other tasks.
But review chairman and MP Frank Field said there was “too few” convictions.
Government figures have previously estimated there are between 10,000 and 13,000 potential modern slavery victims in the UK
The independent review, set up last year to look at potential improvements to the act, is also led by MP Maria Miller and Baroness Butler-Sloss, the former president of the Family Division of the High Court.
Mr Field said modern slavery is “one of humanity’s greatest evils” that exploits “the most vulnerable people in our society”.
It “pervades every country in the world and every community of the United Kingdom”, he said.
In a foreword for the report, to be published on Wednesday, Mr Field said the “world-leading” act gives law enforcement agencies the tools to tackle modern slavery offences.
“But there are still sadly too few convictions being handed down for the new offences prosecuted under the act, and too few Slavery and Trafficking Prevention and Risk Orders are in place to restrict offender activity,” he said.
The 80 recommendations were made across four areas: the role of the independent anti-slavery commissioner, transparency in supply chains, independent child trafficking advocates and the legal application of the act.
Baroness Butler-Sloss said: “We urge the government to respond quickly to the recommendations we have made, bringing new legislation into effect wherever necessary, and adding teeth to that legislation which already exists.”