The UK economy would take a £328m hit if all migrant workers stayed at home for a day, new research says today.

The nation’s daily GDP would fall by 4 per cent if all non-British citizens stopped working for 24 hours, according to the New Economics Foundation (NEF).

Its report also highlights how no less than 26 per cent of health professionals are migrants – far more than the average of 10.9 per cent of the UK’s total workforce.

Most starkly, it concludes: “If all migrant workers stopped working for the day, the NHS and other key parts of our economy would be unable to function.”

The study has been published to coincide with a day of action across the country to illustrate how much immigrants contribute to the country.

Events are planned for “One Day Without Us” in England, Scotland, Wales and Northern Ireland, at university campuses, town centres and private businesses.

The study also comes on the day that the House of Lords begins debating the Article 50 Bill, when peers will attempt to guarantee the rights of three million EU citizens in the UK after Brexit.

Marc Stears, the NEF’s chief executive, said: “Britain has a long and proud tradition of openness to people from overseas and our research conclusively shows that migrants have more than repaid for the welcome they have received.

“Our future as a country depends on the economic, cultural and social contribution that migrants make.

“As countries all around the world succumb to the siren call of populism, we need to remember that contribution and to celebrate it.”

A number of businesses will close today to make the point that Britain couldn’t manage for even one day without the contribution of migrants.

They will include a jewellery shop in Edinburgh owned by Uta Rosenbrock, a German citizen, who said: “I have, over the years, employed women from Australia, Canada, Czech Republic, Slovakia, Poland, Spain and of course Scotland.

“I have taken pride in being part of a vibrant, multicultural community in Edinburgh. Never have I questioned my right to be here, all my adult and working life has been in Scotland.

“Now, suddenly, all of that is in question. I am closing my shop on 20 February so the community see what they stand to lose if we all leave.”

In the Commons, a threatened Tory rebellion to guarantee EU nationals’ rights evaporated when Amber Rudd, the Home Secretary, insisted “nothing would change” without MPs’ consent.

However, that means the uncertainty facing EU citizens will continue unless and until Ms May agrees a deal with EU leaders when the exit talks get underway in April.

Peers across parties are confident they can force MPs to think again by passing an amendment to deliver an immediate unilateral guarantee of protected rights.

Today will also see MPs debate a 1.85 million signature petition against US President Donald Trump’s planned state visit to the UK. It will be followed by a demonstration outside Parliament over his attempt to ban travellers from seven mainly Muslim countries entering the US.