Approximately a million undocumented migrants living under the radar in the UK could be at risk not only of contracting Covid-19 but also of starvation because of the crisis created by the pandemic, charities have warned.

Nobody knows exactly how many of these migrants are currently in the UK, as the Home Office does not have comprehensive records of their whereabouts. This group includes asylum seekers whose claims the Home Office has rejected but who are fearful of returning to their home countries and temporary workers whose visas have expired.

A report published in November 2019 by the Pew Research Center, a Washington thinktank, estimates that there could be between 800,000 and 1.2 million of these migrants currently in the UK.

Asylum seekers with an active claim receive meagre support from the Home Office – £37.75 per week – to buy food and other essentials and no-choice accommodation. However, the vast majority of those whose cases have been refused receive no support at all.

They are not allowed to work and survive thanks to a network of charities who provide survival packages of cooked meals at day centres, food parcels, secondhand clothing and supermarket vouchers. However, these charities have closed their day centres because of the pandemic.

Mohammed, 30, was refused asylum despite coming from Eritrea, where the Home Office will not send people back to. He is based in London and says he is “desperate and struggling to survive” during the pandemic.

“Every place where we got support is closed now. My friend gave me a bike because I have no money for bus fares. I’m cycling round everywhere looking for food but can’t find anything. If I can just find enough food to eat once a day, I think I will survive but I have not managed to find very much to eat.

“I’m not worried about coronavirus, I will accept whatever comes into my life with the virus. But I am worried that I will die from hunger.”

John, a 30-year-old from Cameroon who was refused asylum, lives in Manchester and said the virus had caused a lot of panic among migrants.

“All of the charities and the churches where I used to go to get help with food and other support are shut down now. I was sleeping at Victoria or Piccadilly Stations but the charity RAPAR that I’m a member of has found me some temporary accommodation. I can’t return to my country because the military is killing people there. We are all in a state of trauma.”

RAPAR’s chair of trustees, Dr Rhetta Moran is calling on the government to support undocumented, displaced and destitute people – those most vulnerable to Covid-19 – to come forward for safe housing without fear of being locked up.

Haringey Migrant Support Service has created an emergency fund for its homeless and destitute migrant visitors who they were previously supporting with food bank vouchers, food parcels and clothes. They were also providing lunch at their drop-in centres, which are not currently operating during the pandemic.

Open letters from dozens of NGOs are currently circulating, calling on government to provide support for destitute migrants. The Public Interest Law Centre, Project 17, Migrants’ Rights Network and others have produced an open letter to councils calling on them to establish Covid-19 homeless task forces for this group catering for such people.

It is unclear whether an initiative due to be announced on Monday to house homeless people in empty hotels will include destitute migrants or only British street homeless people. The latter have access to housing and other benefits, the former do not.

A government spokesperson said: “Nobody should find themselves starving in this crisis – and many charities will be supported through the measures the government has outlined to keep people employed.

“We understand that this is a difficult time and we are continually reviewing the situation to consider what more can be done for those in the UK whose immigration status has been affected by coronavirus.”