Trade unions have criticised the Government’s decision to press on with measures to get people back into the office, despite putting the brakes on other lockdown easing plans.

Under the new guidance, which came into force on August 1, employers can now ask their staff to return to the office if they have implemented coronavirus-control measures.

Previously the Government had been asking everyone to work from home where possible.

The guidance state that even those deemed “extremely clinically vulnerable” to the virus can be asked to return to work if they cannot work from home.

It advises vulnerable individuals be offered the “safest available on-site roles” or temporarily adjusted working patterns.

The Prime Minister’s official spokesman said: “For a lot of people working from home does work, but if employers and employees think that you need to get into the office to be more productive, that is a very, very important consideration.”

Monday is the first working day the rules have been in place.

Other planned lockdown easing measures, such as the opening of casinos, bowling alleys and skating rinks and wedding receptions of up to 30 people, have been put back by at least two weeks.

Heads of civil service departments were told in late July they should be “accelerating” their employees back into the workplace.

Civil service head Alex Chisholm said in a letter to all permanent secretaries it was time to “change the default that civil servants should work from home, and accelerate the return to the workplace from August 1”.

But the Public and Commercial Services Union (PCS) accused the Government of “playing fast and loose” with workers’ safety.

PCS general secretary Mark Serwotka said: “No-one should be returning to a workplace until it has been made safe to do so.

“Current scientific advice is that people should work from home where they can.

“Boris Johnson is risking industrial unrest by pursuing this policy and our union will support members who believe their workplace is unsafe to return to.”

Dave Penman, general secretary of the FDA Union, which represents managers in the civil service and public servants, accused the Government of co-opting civil servants into “virtue signalling”.

He tweeted on Monday: “The majority of civil servants are currently working successfully from home.

“Ministers need to recognise this and allow the civil service to manage this transition, without pressure to virtue-signal for a pattern of working that has already changed for good.”

The PM’s spokesman said: “We have removed from the guidance the default that people should work from home where they can.”

He added that individual permanent secretaries and other senior civil servants “should be having conversations with their teams about how best they can be working”.

Asked if the Prime Minister – who is set to spend time in Chequers this week – was following his own guidance, the spokesman said: “The PM has meetings in No 10 both this morning and this afternoon and the PM does work from Chequers. That’s always been the case.”

Transport union RMT criticised the Government for its mixed messaging – simultaneously urging people back to work, often via public transport, while tightening lockdown measures in some part of the country.

RMT senior assistant general secretary Mick Lynch said: “This is a high risk strategy and at this critical time no one should be gambling with the safety of ‎passengers and staff.”

Prospect, a union which represents people from a range of professions in both the public and private sectors, cautiously welcomed the move as long as a return to office working was “flexible and safe”.

General secretary Mike Clancy said it was up to the Government to provide leadership and clarity.

“This means ensuring the Health and Safety Executive is properly funded after a decade of cuts, providing security for workers facing local lockdowns or further spikes in infection rates, and by sorting out the sorry mess which is how it communicates with the public,” he said.

The Institute of Directors (IoD) believes very few office-based firms would be in a rush to get their staff back into the workplace.

Research conducted in May of almost 1,000 business leaders found four fifths said they planned to keep increased flexible working such as working from home for their office-based employees.

Edwin Morgan, the IoD’s director of policy, said it was hard for businesses to know “whether they’re coming or going”.

The IoD is now calling for the Government to set up a recovery fund to help small firms return to the workplace safely.