But Mace has decided to pause all of its jobs for at least another week under a “rolling suspension”.

Restarted BAM projects include existing sites “critical to the national Covid-19 effort” and “new projects to build emergency Covid-19 wards.”

BAM said the pause allowed it to carry-out “extensive checks and agreements with our project teams, clients and supply chain” to ensure work could continue under social distancing guidelines.

BAM said: : “Our teams around the country have been reviewing and redesigning work at all sites.

“This has allowed discussions to be had with our clients, subcontractors and those employees who are willing and able to work at sites, about re-opening.

“To support this, we have significantly reduced the number of people who will be present on our sites to help us work safely.”

BAM sites still closed are predominantly in Scotland, London and the Midlands where the company said it will “continue to work on how these can be safely re-opened at a future date.”

BAM said: “We have also been working closely with the NHS, Department for Health and the UK Government on numerous critical healthcare schemes around the country, building new facilities or adapting current facilities to treat Covid-19 patients.

“Across the country, our Facilities Management teams continue to provide essential buildings management, cleaning and catering services to the emergency services, local authorities and those schools remaining open for key workers’ and vulnerable children.

“In order to maintain services, and where possible BAM FM employees that serve private sector clients are re-deploying to fill roles serving the public sector that are unfilled due to illness or self-isolation.”

BAM Construct UK Chief Executive James Wimpenny said: “Buildings are central to people’s lives, and at this time they are also central to saving people’s lives.

“These are the most extraordinary and concerning times for us all.

“We are all in this together, working hard to save lives and livelihoods.  I want to thank everyone at BAM for everything they are doing to keep themselves and their families safe, and for responding so well to rapidly changing circumstances.”

A Mace spokesperson said: “The Government has been clear that construction work should continue where it can do so in-line with guidance from Public Health England.

“Mace has been working over the last week to understand what measures we would need to introduce in order to open our projects safely.

“Although it is clear that some projects can operate under these conditions, we are not yet certain we can do so without putting people at risk.

“As such, Mace will now introduce a rolling, temporary one-week suspension of all site activity. This suspension will now be in place until at least Tuesday 7 April.

“It will be reviewed regularly as the situation develops to understand what, if any, work can be carried out safely.

“Regrettably, that means that no construction work will take place this week, other than safety critical work or activities required to protect or secure construction projects.