All EU nationals currently living in Britain will be allowed to stay following Brexit, after the Home Office discovered that five in six could not legally be deported.

There are around 3.6 million EU citizens living in the UK, more than 80 per cent of whom will have permanent residency rights by the time Britain leaves the union in early 2019, official research has concluded.

The remainder – more than 600,000 people – will be offered an amnesty, with several Cabinet ministers telling The Telegraph that those citizens will be offered the right to stay permanently, in a policy that may prove controversial.

Theresa May, the Prime Minister, has refused to guarantee the rights of EU citizens currently living in the UK, saying she believes that the Government must not “reveal its hand” ahead of Brexit negotiations, which will begin when she triggers Article 50 next year.

Once an EU citizen has been in the UK for more than five years, they are given permanent residency rights.