The move highlights the government's delicate balance between protecting the economy and preventing the virus's spread, coming at the same time as the announcement of quarantine on arrivals from France and tougher penalties for those refusing to wear masks.

Last month, amid rising case numbers, Johnson said there was "a warning light on the dashboard" and paused the reopening of casinos, bowling alleys and skating rinks.

On Friday, he said that phase of his reopening plan could now go ahead.

"Today, we are able to announce some further changes which will allow more people to return to work and the public to get back to more of the things they have missed," he said.

Most businesses are now allowed to operate, albeit within strict guidelines. Friday's announcement means trials of crowds at sporting events can also go ahead and indoor theatre, music and performances can resume with socially distanced audiences.

The Office for National Statistics said a small increase in the percentage of people testing positive for COVID-19 in July had now levelled off, although some said this was not the primary driver for the lockdown easing.

"I don't think it's really been taken on epidemiological grounds, I think it's really been taken primarily for economic reasons," John Edmunds, one of the scientists advising the government on its pandemic response told BBC radio.

Johnson also announced increased fines of up to STG3200 pounds ($A5480) for those who repeatedly refuse to wear a face mask where they are required to do so, and cautioned that he would halt the lockdown easing again if required.

"Most people in this country are following the rules and doing their bit to control the virus, but we must remain focused and we cannot be complacent," he said.

Australian Associated Press