Senior Leave backers express concern over approach to immigration and say students should be free to come to UK

The biggest donor to the Brexit campaign has called on Theresa May to unilaterally guarantee the rights of millions of EU nationals already in Britain.

Peter Hargreaves, the billionaire who donated £3.2m to the Leave.EU campaign, said that the prime minister should reassure the three million EU nationals already in the UK that their current rights would be maintained.

Hargreaves, who is now retired after founding the Hargreaves Lansdown financial services company, said he understood the reluctance to guarantee the rights of EU nationals before the delicate negotiations over Brexit. However, he said, May should simply “make the gesture” and not wait until Brussels agreed to do the same for UK nationals living in EU states.

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“People who are doing great jobs in this country are feeling insecure and I think it would be really good for those people to have the comfort that we are not going to boot them out in 18 months’ time,” he told the Observer. “I just think we should make the gesture, full stop. I don’t think there should be a quid pro quo, I just think we should make the gesture. They would look pretty churlish if they didn’t [reciprocate by guaranteeing the status of UK nationals in the EU].”

His intervention comes after a week in which Brussels officials expressed concern over reaching a deal on the status of EU nationals in the UK. Brussels is insisting that they are allowed to keep all their rights, including access to healthcare and the right to bring a spouse to the UK.

It coincides with concern among some senior Brexit backers over May’s approach to immigration after Brexit.

Simon Wolfson, the Tory peer and Next boss who donated £50,000 to Vote Leave, warned that May must not send the signal that Britain will “pull up the drawbridge” after Brexit.

Meanwhile, Paul Marshall, the hedge fund manager who gave £100,000 to Vote Leave, urged May to remove foreign students from official immigration figures. She has refused to back the idea, despite pleas from Conservative MPs and universities.

Hargreaves said he was happy to see EU nationals already here maintain their current rights. “Most of those are in work and adding to our economy,” he said. “We are going to be very selective about who we let in in the future, but I think there should have been that comfort given, because they came under different circumstances.”

Wolfson told the recent Prosperity UK conference on Brexit that foreign workers needed to be seen as “an asset to our economy”. He criticised any attempt to impose “arbitrary numbers” on the number of migrants the UK should accept each year. May has suggested she still wants a reduction of net migration to the “tens of thousands”.

Wolfson said: “While it is important and essential that Britain controls who comes into this country, and it is important that we have the services and infrastructure to deal with an increase in numbers … it is vital that we do not pull up the drawbridge.

“We are in a period of record immigration and we have the lowest levels of unemployment on record since the war. If we are too draconian on immigration, it will have two adverse effects on our economy. The first is it will undermine all of our quality of life and undermine growth, and the second is it will send the worst of all possible signals to the rest of the world.

“The most important thing to come out of Brexit is sending a very clear message to the rest of the world – that Britain is an open country, a free trading country, one that embraces the rest of the world and does not reject it.”

Marshall said that the government should stop counting foreign students in migration figures, arguing that universities “must lie at the heart of any strategy for creating a prosperous post-Brexit economy”.

“It is essential that we continue to encourage the free flow of international students and research and it is a no-brainer to take students out of the migration numbers,” he said.

“Polling of Brexit voters even shows strong support for this change. People in the north and Midlands fully understand the logic of supporting the university sector. They are simply not worried about student migration.”