Boris Johnson clashes with Theresa May after demanding amnesty for all long-standing Commonwealth immigrants

Experts at Oxford University warn scandal - provoked by prime minister's crackdown - extends 'well beyond' the Windrush generation

Boris Johnson has clashed with Theresa May after calling for an amnesty for all long-standing immigrants from the Commonwealth, as experts warned the scandal extends “well beyond” the Windrush generation.

The Foreign Secretary is said to have become “very agitated and annoyed” at a bad-tempered Cabinet meeting – as the prime minister appeared to reject his proposal.

Mr Johnson is understood to have warned that many other people who moved to Britain from other Commonwealth countries decades ago would be trapped by the crackdown which triggered the Windrush debacle.

They also faced mistreatment unless they could produce difficult-to-obtain evidence to show that they have lived in Britain and have the right to remain.

That warning has been echoed by experts at Oxford University, which said the tough immigration rules were also hitting people from non-Windrush nations.

“The issue of citizenship and residence rights for Commonwealth migrants in the UK Commonwealth who arrived before and during the early 1970s does not just affect those from the Caribbean,” said Robert McNeil, deputy director of the Migration Observatory.

“Tens of thousands of people from other Commonwealth countries in Asia, Africa, the Americas and elsewhere may also be in the same boat.”

The Migration Observatory has estimated there are 13,000 people from India facing that situation – almost as many as the 15,000 Jamaicans.

At Cabinet, Mr Johnson urged the prime minister to go further than the effective amnesty for the Windrush generation, promised by Amber Rudd, the home secretary, The Spectator magazine reported.

The offer should be made to anyone from the Commonwealth – or elsewhere – who had been in Britain for many years, other than those with a criminal record.

It said Ms May remarked “acidly” that he had twice called in the past for an amnesty for all immigrants, proposing the help for people who had been in Britain for more than a decade.

It is suspected that Cabinet ministers with a more liberal approach to immigration believe the Windrush fiasco provides an opportunity to press their case against Ms May’s hardline stance.

Also in their sights, is the failed and widely-ridiculed policy of reducing net migration to “tens of thousands” and the inclusion of foreign students in the migrant total.

The clash was also Mr Johnson’s second direct challenge to the prime minister, after he called, last week, for police to use stop-and-search powers more – a second policy she has resisted.

In a further sign of rancour, the prime minister is also reported to have admonished ministers for briefing journalists about Cabinet splits over leaving the EU customs union after Brexit.

On Monday – in a bid to defuse the Windrush row – Ms Rudd announced fast-track citizenship for all those affected, as well as the waiving of huge fees.

The Home Office, which has set up a taskforce and a hotline, has said that help will be provided to people from all Commonwealth countries, rather than simply Caribbean nationals.