Mass testing for coronavirus in Liverpool is showing positive signs, the city’s public health director said, as thousands of people were tested on the first day of the pilot scheme.

On Friday, queues built up outside the new test centres which opened at midday, with people waiting around 45 minutes outside the Liverpool Tennis Centre – one of the six facilities – before it opened.

The programme aims to test up to 50,000 people a day once fully operational, Liverpool director of public health Matt Ashton said.

On Saturday, he told BBC Radio 4’s Today programme: “It was the first day yesterday and we didn’t open first thing, we opened at lunchtime and had six of the asymptomatic testing centres open.

“We are still working on the numbers but we think (there were) about 1,500-2,000 people per testing centre, so really good numbers and really good interest, so it was very encouraging.”

He said he thought an English lockdown had been necessary because the Tier 3 restriction had not been getting coronavirus transmission under control “by itself”.

“The restrictions will absolutely help, they will reduce the levels of infection in our community because they will cut social contact,” Mr Ashton added.

“The big question is will they cut them enough, will it take the levels of the virus low enough?”

He had previously said there was capacity for 85 centres to be set up by the end of the pilot scheme, which is due to last for 10 days initially, with the prospect of it being extended.

The facilities, set up at the Exhibition Centre Liverpool and at council-run sports centres, are providing lateral flow tests with a turnaround time of under an hour, for people who live and work in the city and do not have symptoms.

The scheme has drawn criticism from some health experts who have branded it not fit for purpose, with Allyson Pollock, professor of public health at Newcastle University, warning that plans to test asymptomatic people went against advice from the Scientific Advisory Group for Emergencies (Sage) to prioritise testing for those who were displaying symptoms.