Britain will end the free movement of labour immediately after Brexit and introduce measures to drive down the number of lower-skilled EU migrants, a leaked government document published by the Guardian newspaper said today.

Reducing net migration to Britain was one of the main reasons behind last year's vote to leave the European Union, but firms have expressed concerns they may not be able to hire the skilled and unskilled workers they need after Brexit.

The interior ministry was not immediately available for comment on the document, which the Guardian said had yet to be endorsed by Prime Minister Theresa May's top team of ministers.

"Put plainly, this means that, to be considered valuable to the country as a whole, immigration should benefit not just the migrants themselves but also make existing residents better off," the Guardian quoted the document as saying.

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May has previously said that free movement of labour would have to end when Britain leaves the bloc, but she has so far offered no detail on what kind of immigration system she wants.

The Guardian said the government was also outlining a phased introduction of a new immigration system that ends the right to settle in Britain for most European migrants – and places tough new restrictions on their rights to bring in family members.

In August, net migration to Britain fell to its lowest level in three years in the 12 months to the end of March, with more than half the drop caused by EU citizens leaving and fewer arriving since the Brexit vote.

But, at 246,000, the figure is far higher than the "tens of thousands" May has repeatedly stressed she believes is a sustainable level of migration.