The UK risks becoming a “backwater” for scientific research unless the world’s “brightest and best” are made welcome after Brexit, top scientists warned today.

Newly-appointed fellows of the Academy of Medical Sciences told the Evening Standard of their concern at the impact of EU exit on the UK’s “superpower” status.

They called for changes to the immigration system to retain EU staff already in the country – and to encourage future generations of “exceptional talent” to the UK.

And they urged future co-operation between the UK and EU on life sciences regulation, and for the Brexit deal to allow British experts to continue to access EU research funding.

The Academy’s new intake of “star scientists” told the Standard of their fears that a “Hard Brexit” will cause a “brain drain” of European colleagues already in the UK.

London’s top universities have suffered rejections from Continental applicants for “senior posts” on several occasions since last June’s referendum, the Standard has learned.

The UK’s inability to lead multinational research projects after Brexit is also seen as a key concern. This could curtail pioneering new cancer and gene-editing therapies being offered on the NHS and limit the UK’s influence in global projects such as the search for a HIV vaccine, the fellows said.

It came as Professor Lee Cronin, Regius chair of chemistry at Glasgow university, warned: “Brexit threatens the foundations of UK science.” Writing in today’s Standard, he said: “Without action, Brexit will cause the UK to lose its global science status very quickly.”

One of the Academy’s new fellows, Professor Robin Shattock, who is leading a EU-funded search for the world’s first HIV vaccine at Imperial College London, said UK researchers would no longer be “calling the shots intellectually” after Brexit.

He said: “Increasingly, big medical problems are solved by big collaborative teams. Whatever Brexit deal the UK manages to negotiate, I expect that UK researchers will not be able to lead pan-European projects. It would be unprecedented to have a pan-European consortium funded through the EU being led by a non-EU member.”

The 22 million euro HIV project involves 22 EU institutions, with Imperial receiving about a quarter of the cash. “We are funded until 2020,” Professor Shattock said. “Beyond that, we are going to become a backwater in terms of leading large multi-centre programmes.”

He said that while Brexit might not delay the discovery of a vaccine, “it means it will be very hard for UK investigators to maintain a world lead or to be internationally competitive”. About two million people a year contract HIV. The annual cost of treating them is about £15 billion and rising.

Professor Robert Wilkinson, of the Francis Crick Institute, which has staff from more than 70 countries, called for a “simple, swift post-Brexit immigration system for skilled researchers, technicians and innovators irrespective of origin – so that the UK maintains its place as a world-leader in global science”.

He said: “This could take the form of a wider reform of the Tier 1 visa system to make it more appealing to leaders and exceptional talent.”

Professor Tom Williams, an expert in genetic blood disorders at Imperial, said many UK universities were heavily reliant on European applicants for PhD and more senior academic positions. There are 31,000 non-UK EU citizens working in academic research in the UK.

Professor Williams said: “The Brexit vote has created deep anxiety in many of our colleagues regarding their longer term future and the way that many are increasingly perceiving themselves as unwelcome. 

“The loss of access to EU funding streams would devastate many academic departments that rely heavily on these funds. Freedom of movement for academic professionals and access to EU funding streams should both be at the top of the list for future negotiations.”

In 2015, UK-based researchers received 1.2 billion euros from the EU’s Horizon 2020 fund, the biggest-ever fund for scientific discoveries.

According to Innovate UK, the UK receives 3.2 per cent of global funding for research and development but is responsible for a sixth of scientific breakthroughs, making the sector an “unparalleled strategic asset” for the UK.

The previous Tory Government offered to underwrite grants already awarded by the EU, but not to increase funding to the sector, though Theresa May regards the UK As a “world-leader in science and research”.

Professor Sir Robert Lechler, provost of King’s College London and president of the Academy of Medical Sciences, said his Italian wife, Giovanna Lombardi, a professor of immunology at King’s, had felt “less at home” since the Brexit vote despite being a UK resident for 30 years.

He said of the various concerns sparked by Brexit, “the most important by far is people”. He added: “We need to make sure our international scientists feel secure here now.”

He pointed to advances in psychiatry, genomics, gene editing and immunology – offering solutions for inherited defects and cures for cancer – as examples of how the UK led the field in medical sciences.

“That depends on having the best people and having the best partnerships and having sufficient resource,” he said. “If we start losing ground on that, then we will no longer be at the forefront and people will no longer get the best treatments at the earliest opportunity, delivered by the best staff.”

Matthew Hotopf, a professor of psychiatry at King’s College London, leads a 25 million euro project, RADAR CNS. This involves eight EU nations and the US researching whether wearable devices can help prevent and treat depression, multiple sclerosis and epilepsy.

Professor Hotopf said: “It’s very concerning for our position as leaders of European science. We gain more funding than we put in, and lead a lot of major projects.

“One thing the EU has done is provide a platform for very big science projects. [RADAR] involves 23 different centres, including five major pharmaceutical companies.

“The really tricky thing is that we just don’t know what is going to happen, and the uncertainty is already damaging our role and impacting our ability to take the leadership of projects.”

He added: “People talk about Hard Brexit or no deal at all. I think a lot of people who voted Brexit probably didn’t appreciate we would be considering coming out of the EU without any kind of agreement.

“I think the critical thing is making a very clear commitment to supporting our colleagues who are EU nationals working in UK science and research.”

Professor Dorothy Bennett, director of the Molecular and Clinical Sciences Research Institute at St George’s, University of London, said Brexit ran “counter to the international and collaborative nature of today’s science”.

She said: “EU funding has taught us to work together well and design large and ambitious projects with our European friends, and I hope very much that such opportunities will not be lost. 

“Many of our colleagues working in the UK are from overseas, including the EU. We (UK scientists) and they are impatient to hear any kind of reassurance as to their security of permission to remain and work – likewise about the security of British scientists working in Europe.”

Dr David Roblin, of the Francis Crick Institute, said collaboration was “how science works at its best, how ideas arise and discoveries are made, and ultimately how society and the economy will benefit the most through new treatments for disease”.

The Conservatives pointed to plans announced in the last Budget that included £90 million for 1,000 PhD places and £210m for new academic fellowships, including in bioscience and biotechnology. That followed £4.7 billion of new investment in research and development announced in the Autumn statement.

Chancellor Philip Hammond said: “One of our key objectives for Brexit is to be the best place in the world for science and innovation – which is why we are investing £4.7 billion in research and development, including £300 million announced in the Budget to support the brightest and best research talent.

“If Jeremy Corbyn is Prime Minister on 9 June, leading our Brexit negotiations, there is no chance of that. Only a vote for Theresa May and her local Conservative candidate can deliver for Britain’s world-renowned science sector in the Brexit talks.”