The British government should end uncertainty for EU nationals living in the UK by promising that those based in the country when article 50 is triggered can stay, according to a report compiled by both sides of the Brexit debate as well as employers and unions.

Those who can also show they have lived in the UK for five years should be offered permanent residency, with continued rights for a period to bring in family members and to claim benefits, the study said.

It also urged the government to streamline the process for residency applications, amid calculations that at current rates it would take well over a century to deal with all the EU nationals living in the UK.

Set up by the British Future thinktank, the report was chaired by the leading pro-leave Labour MP Gisela Stuart, and also featured panellists from the Conservatives and Ukip, as well as the TUC and Institute of Directors.

Defining the rights and status of the estimated 2.8 million EU citizens living in the UK should be “the first priority of this government in its negotiations with other EU member states”, Ms Stuart said.

The government has said repeatedly it could not offer guarantees until the post-Brexit status of the estimated 1.2 million Britons living elsewhere in the EU is agreed.

However, the report noted that since almost no one had suggested that EU nationals in the UK might have to depart – with even the official Vote Leave campaign arguing their status should remain the same – such prevarication was pointless.

“Britain should make clear at the start of the Brexit negotiations that EU citizens already here before that date can stay,” Ms Stuart said. “This would send a clear signal about the kind of country the UK will be after Brexit and the relationship we want with Europe. We should expect reciprocal deals for Britons living in European countries, but Britain should make the first move to demonstrate goodwill.”

Those given such a guarantee should comprise all those living in the UK on the day article 50 is triggered, or when another formal mechanism is invoked by the government to confirm it is leaving the EU, the report says.

It recommends that those who can show five years of residency be given permanent residence, to be converted to a new form of indefinite leave to remain once the UK quits the EU altogether. Help should be given to people such as the self-employed who might find proving residency difficult.

Those who qualify would be allowed to claim things like benefits and student loans, and keep the same rights to bring in family members, for a suggested five-year transition period, it recommends.

The report also urges the Home Office to examine how it could best process so many applications, which the report said would take 150 years to deal with at the current speed of work.

The Home Office has previously confirmed it is trialling a fast-track online system to handle the expected surge in permanent residency applications.

Guardian