UK's Boris Johnson pledges post-Brexit migration controls

Broadly, these kind of systems allow in migrants who meet certain criteria such as qualifications, occupation and language skills. "We must be much more open to high-skilled immigration such as scientists," Johnson said.

"But we must also assure the public that, as we leave the EU, we have control over the number of unskilled immigrants coming into the country.

"We must be tougher on those who abuse our hospitality. Other countries such as Australia have great systems and we should learn from them." Johnson was a leader of the campaign to leave the EU during the 2016 referendum, and a key promise was to "take back control" of Britain's borders. While it remains a member of the EU, Britain is subject to rules allowing the free movement of workers around the bloc.

May's government says EU and non-EU migrants should be treated the same after Brexit -- an approach Johnson backs -- but is still consulting on the details of a new system.

May has however rejected a strictly points-based system, saying it allowed in anyone who met the criteria, providing no control over numbers. And campaign group Migration Watch UK criticised Johnson for not promising migration would fall.

"There is no mention whatever of reducing net migration, let alone how it might be achieved," said group chairman Lord Andrew Green.

For non-Europeans, Britain currently has a complicated system of visas based on skills, minimum salary requirements, the need for a job offer, and in some areas has a numbers cap.

Johnson said the government's independent advisory committee would thrash out the details of his policy, to be introduced from 2021.

But he said would-be migrants should have a firm job offer, speak English and be vetted, and any system should be "fair to people living here".