The rate of coronavirus transmission in the UK is still low, despite earlier fears of regional spikes, a top Government scientist has insisted.

Sir Patrick Vallance, chief scientific officer, said the R rate was below one nationally, after concerns last week that it may have climbed above that in certain regions, but still urged caution as lockdown is eased.

Last week, a report from Public Health England and Cambridge University estimated the value was at 1.01 in the North West, and 1.00 in the South West.

Sir Patrick told Wednesday’s Downing Street briefing: “The R is below one, but perhaps only just below one.

“The epidemic is shrinking, but not fast. Numbers are coming down but are not yet very low.”

He added: “That urges caution, it urges going slowly with changes and it urges measuring very carefully to see the impact and being prepared to reverse things where measures have been taken that have an impact on this, and importantly means looking for outbreaks locally and dealing with those fast.”

The scientist’s caution was echoed by chief medical officer Professor Chris Whitty, who described the UK as being in the “middle” of the epidemic, not the end.

The comments came after Prime Minister Boris Johnson announced a further small easing of the lockdown rules, allowing single-adult households to form a so-called support bubble from the weekend.

Sir Patrick also suggested the two-metre social distancing measures were not a hard and fast “scientific rule”.

It is wrong to portray this as a scientific rule that says it is two metres or nothing

When asked whether the restriction may be changed to one metre as schools try to welcome back pupils, the scientist said: “It is not a rule, it is not a scientific rule – it is a risk-based assessment on when risk reduces.

“And the risks are associated with distance – so the risk falls after two metres – time, what mitigating factors you can put in place, which can include whether you are sitting side-by-side, back-to-back or face-to-face, whether you’ve got face covering, whether there is ventilation and other measures.”

He added: “It is wrong to portray this as a scientific rule that says it is two metres or nothing – that is not what the advice has been and it is not what the advice is now.”