The reproductive rate of coronavirus is close to one in parts of the country ahead of the partial easing of lockdown measures, the UK Government’s chief scientific adviser has said.

Sir Patrick Vallance told Thursday’s Downing Street press conference that the country was in a “fragile state” and that measures will need to be eased carefully.

Prime Minister Boris Johnson announced that the Government’s five tests required for the next phase of restrictions to begin have been met, which included reducing the rate of infection to manageable levels across the board.

Sir Patrick warned the public should expect local outbreaks of the virus and that there were currently about 8,000 new cases per day.

He said: “That is not a low number, so it’s worth remembering that we still have a significant burden of infection, we are still seeing new infections every day at quite a significant rate and the R is close to one.

“That means there is not a lot of room to do things and things need to be done cautiously, step by step and monitored, and the test and trace system needs to be effective in order to manage that.”

The R-value – the average number of people that will contract coronavirus from an infected person – was said to be between 0.7 and one across the UK in the last two weeks of figures.

However, the upper band has since decreased to 0.9.

This is not a time to say everything's OK, we're releasing measures, everything's going to be rosy

There is a time lag in the calculations, with the latest R-value figures relating to what was happening two to three weeks ago.

The latest data on the R-value is set to be published on Friday.

Explaining the crucial statistic ahead of the relaxation of the measures, Sir Patrick said: “If the R is one, those numbers stay at that high level, whereas of course what we’ve got to do is get them down.

“So we need to keep concentrating on R below one, that means making sure that the measures that are in place are adhered to and that we all stick with them to make sure that the right thing is done, and that the numbers come down and that we end up in a position where we can get the numbers down and the R down a bit, but we’re at a fragile state.”

Sir Patrick was asked about the R-value after figures showed the rate was close to one in parts of Northern Ireland.

He said: “The R remains below one everywhere, but you’re quite right it’s very close to one in some places.

“Both in terms of nations, but also in terms of places within those nations, there may be in areas where the R is very close to one.

“That’s why, as I laid out, we’ve got to be very cautious. This is not a time to say everything’s OK, we’re releasing measures, everything’s going to be rosy.

“It’s a time to go very cautiously with changes as they take place, monitored very carefully, being prepared that there will be local outbreaks – because there will be – and being prepared that, therefore, recommendations would come to reimpose measures and I think that’s the world we’re in.”