Image copyright Science Photo Library

The UK visa system is enabling unscrupulous employers to treat foreign workers as modern-day slaves, a BBC investigation has found.

BBC Radio 4's Face the Facts spoke to dozens of workers who were paid little or nothing, were not allowed out and were sometimes abused or beaten.

The situations come from "tied" visas - meaning the right to be in the UK can be withdrawn by the employer - and "transit" visas on fishing boats.

Ministers said a review was under way.

Transit visas are being used to bring in recruits to the fishing industry who have no right to set foot on dry land - and therefore no access to UK employment rights.

Face the Facts found this led to some fishing workers spending weeks at a time at sea, sometimes unpaid, sleeping in cramped conditions, often physically and verbally abused.

With tied visas, employees must stay with the employer they arrived to work for - so if they are mistreated and run away, they are likely to be deported.

Modern slavery minister Karen Bradley said: "We do know that there are problems; that's why I've just commissioned an independent review of the visa arrangements for overseas domestic workers."

The government's Modern Slavery Bill, which has cross-party support, will not affect tied or transit visas.

But Ms Bradley said it was the boldest attempt yet in Europe to tackle human trafficking and slavery

It will increase the maximum sentence to life imprisonment, introduce an anti-slavery commissioner and give courts new powers to order compensation.

Face the Facts is broadcast on Radio 4 at 12:15 GMT.