Former health secretary Jeremy Hunt has added his voice to those of disease experts calling for medical grade masks to be compulsory on public transport and in shops.

Some epidemiologists fear that cloth masks, which are often home made, are not sufficient to deal with the new strains of Covid-19.

Trisha Greenhalgh, a professor of primary care at the University of Oxford, said “the context has changed” over the course of the pandemic and everyone should be wearing medical-grade coverings.

Prof Greenhalgh tweeted on Sunday: “Double-layer cloth masks seemed OK when a) supplies of PPE were very low, b) virus was less contagious, c) incidence was lower.

“The context has changed. We need to be wearing medical-grade.”

Mr Hunt retweeted the post, adding: “I agree.”

In an interview with the Observer published on Sunday, the UK’s longest-serving health secretary said: “Current lockdown measures are just not working fast enough.”

He said he wanted to see FFP2 respirator masks, which filter both the inflow and outflow of air, made compulsory in public spaces such as shops and public transport.

Similar measures have already been imposed in Austria and parts of Germany.

Mr Hunt said: “Last time we waited too long before requiring masks, let’s not make the same mistake again.”

He also questioned whether the two-metre social distancing rule is sufficient.

American epidemiologist Dr Eric Feigl-Ding, a senior fellow at the Federation of American Scientists, is also calling for air filtering masks to mandatory in the US.

He tweeted: “Cloth just isn’t enough anymore folks.”