Rishi Sunak has been warned by Theresa May that efforts to tighten modern slavery laws to prevent migrants using them to avoid being deported risk creating other loopholes that could be exploited.

The former prime minister, who championed the “world-leading protections” for victims of modern-day slavery, warned Mr Sunak against unintended consequences in his attempts to prevent the rules being exploited.

The Prime Minister has promised to “raise the threshold someone must meet to be considered a modern slave” and “remove the gold-plating” in the system.

Home Secretary Suella Braverman has claimed the laws are being “abused by people gaming the system” to stay in the UK when they would otherwise face being deported.

The Modern Slavery Act was introduced by Mrs May during her time as home secretary in order to protect vulnerable people from exploitation, domestic servitude or being trafficked for sex.

Mrs May told BBC Radio 4’s PM: “We need to ensure we don’t reduce our world-leading protections for victims of modern slavery.”

She added: “It’s important not – inadvertently – to create another potential loophole.

“So, for example, there’s talk of requiring more evidence from individuals.

“If you’re somebody who’s been trafficked here as a sex slave, and you manage to find your way out of that and look to somebody for help, the chances are you probably haven’t got a piece of paper or a written statement from somebody to say ‘you’ve been in slavery’. The evidence comes gradually.

“If you are somebody who is being brought by a criminal gang who are abusing the system, and they know there needs to be a piece of paper, they probably will provide a piece of paper.

“So it’s making sure that, in dealing with problems that are identified, we don’t create other problems.”

Meanwhile, official figures showed 90 people crossed the English Channel in two small boats on Christmas Day.

They were the first crossings recorded since December 21 and take the provisional total for migrants making the dangerous journey from France this year to 45,756.

Mr Sunak has promised legislation in the new year to help tackle the problem by making sure that if someone enters the UK illegally they do not have the right to stay in the country.

Ministers are also working to tighten immigration rules to curb numbers coming to the country legally.

Home Secretary Suella Braverman has drawn up a plan that would target foreign students, make it harder to bring spouses to the UK, and increase the minimum salaries for companies employing skilled workers, The Times reported.

Under a draft of the proposals, seen by the newspaper, the Government would increase the minimum income threshold for British citizens applying for a family visa.

Currently, a couple must earn at least £18,600 and may need thousands more for any children they seek to bring to the UK.

The plans could also make it harder for overseas students to bring dependants with them.

Immigration Minister Robert Jenrick has previously suggested that the rules around student dependants are “ripe for reform” as he is concerned people are coming to university as a “backdoor way of bringing their families into the UK”.