There are also images that appear to show a lack of social distancing.
Mr Johnson attended an indoor venue called the “Lemon Street Market” to meet vendors and had a meeting over coffee with local employers.
After the images emerged, Brits were quick to criticise the Prime Minister.
One person on social media wrote: “Not wearing a mask, in a cafe, not social distancing!
“Well done Boris! One rule for you one for the sheep!”
Another said: “Still making unnecessary journeys and still not wearing a mask in some indoor places!
“You are a total hypocrite as well as the most mendacious prime minister there has ever been, anywhere!”
A third expressed their fear the images could lead to an increase in people failing to follow the coronavirus guidelines themselves.
They wrote in a tweet: “So the Prime Minister is going around without a mask, potentially spreading a deadly virus.
It also requires “you must put a face-covering back on once you finish eating or drinking” in pubs or cafes.
It is understood that coronavirus is largely airborne and wearing facemasks restricts transmission.
A review by Government is currently underway to determine how much longer face coverings are likely to be needed.
The UK has rapidly rolled out its Cover vaccination programme meaning a large majority of adults are now protected against COVID-19.
In total more than 31.5 million Brits have received at least a first jab of a coronavirus antidote.
The progress has seen daily infections and deaths plunge since the start of the year.
In the most recent figures there were 2,763 new daily infections confirmed by a positive test, a 36.6 percent drop in a week.
Deaths have fallen by 35.5 percent over the past seven days with 45 new fatalities recorded yesterday.
Downing Street has been approached for comment on the pictures which have emerged of the Prime Minister.