It comes after a coroner in Lancashire wrote to funeral directors saying that they should use “a towel, bin liner or something like an incontinence pad” to create a makeshift mask when moving the bodies of those who have died of coronavirus.

Scientists said that those most at risk are people who have caught it from others with a high “viral load” rather than those who were frequently exposed to people with mild forms of the disease.

Willem van Schaik, Professor in Microbiology and Infection at the University of Birmingham, said: “On the basis of previous work on SARS and MERS coronaviruses, we know that exposure to higher doses are associated with a worse outcome and this may be likely in the case of Covid-19 as well.

“This means that health care workers that care for Covid-19 patients are at a particularly high risk as they are more likely to be exposed to a higher number of viral particles, particularly when there is a lack of personal protective equipment (PPE) as is reported in some UK hospitals."

Meanwhile, a survey of hospital chief executives by the Health Service Journal found that running out of PPE is one of their biggest concerns alongside a lack of staff testing and workforce shortage.

The head of an acute trust in the Midlands said they faced “a near revolt amongst my clinical staff” because of the problems with PPE, adding: “They see hazmat suits and FFP3 [masks] being deployed in all scenarios in western Europe and want to know why we aren’t doing the same.”

Thirteen out of the 34 who responded said that they would run out of capacity in their intensive care units by next week if the number of new cases continues to rise.

Mr Hancock has insisted that his department is doing everything that they can and has said that a million masks were ordered over the weekend.

He told the House of Commons: “Having the protective equipment for the staff on the front line especially in the NHS and social care but also in other front line service is very important. We are moving heaven and earth and the military involvement is ramping up delivery of that equipment."

Mr Hancock added that all social care settings should have PPE by the end of the week and a hotline has been set up so people can report if they do not have the equipment it and the Government can identify where it is most needed.

But Pam Parker, managing director of PPS which manufactures medical equipment, said that they have had more orders from abroad and the masks are “being utilised by other countries”.

She said that they offered their services to the health service at the beginning of the pandemic but they were told “everything is in hand” whilst GP surgeries turned away their offers as they did not have budgets for the equipment.

The Milton Keynes based company is beginning to see an uptake in orders from businesses and hospitals in the UK but is currently experiencing logistical problems as they need money to pay for masks upfront.

Ms Parker, who has already given away what stock they had to places in need, said: “The money needed is a drop in the ocean and if we all pull together there is no reason why there should be a shortage of this equipment.”