Making mask-wearing optional on public transport when the end of the government’s roadmap out of lockdown is reached would be an act of “gross negligence”, a trade union has claimed.

       Unite, which represents tens of thousands of public transport workers, has opposed the move which the prime minister is expected to announce later today.

       Boris Johnson is set to confirm that face coverings will no longer be compulsory in shared indoor spaces after 19 July and that social distancing in bars and pubs will come to an end.

       He has previously said that people will have to “exercise judgment” going forward, while housing secretary Robert Jenrick told Sky News that soon the state “won’t be telling you what to do”.

       Bobby Morton, Unite’s national officer for passenger transport, said that the idea that “personal responsibility” should replace government rules is “absolutely ridiculous”.

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       “Rates of infection are continuing to increase and not only does mask wearing reduce transmissions, it helps provide reassurance to drivers and to passengers who are nervous about using public transport,” he said.

       “The idea of personal responsibility and hoping that people will wear masks is absolutely ridiculous.”

       Mr Morton added that Unite members have already reported a spike in passengers ignoring rules on mask-wearing and said that they should remain in place until rates of Covid-19 are “fully under control”.

       But while national government mandates on mask-wearing could come to an end, it’s possible transport companies could continue to make them a condition of carriage.

       A spokeswoman for London mayor Sadiq Khan said that it is “something that we will continue to look at closely”, adding that it’s important to “follow the science” when setting rules for passengers on the capital’s Tubes, buses and trains.

       Mick Lynch, general secretary of the Rail, Maritime and Transport union (RMT), said that discussions are ongoing throughout the industry.

       “Yet again there’s a real danger of the government making up policy on the hoof on critical issues,” he said.

       “Back in the real world, discussions are ongoing at industry-wide level but all parties are having to second-guess what the government will say later today and that is not good enough.

       “All the indications are that the Government are going for a free-for-all, whereas common sense and medical advice seems to indicate that some level of control should remain in place in the public realm.”

       The prime minister’s update is likely to be broadcast from Downing Street at 5pm.