The Government is "absolutely open" to delaying the June 21 unlocking, Matt Hancock said on Sunday in the strongest indication yet that the date for the next step in the roadmap could be put back.

A two-week delay until July 5 has been under discussion by scientists and civil servants, but Mr Hancock’s remarks  confirmed that pushing back the relaxation of restrictions was being considered.

"We are absolutely open to doing that if that’s what needs to happen. We said in the roadmap that June 21 is the date by which we would not take Step 4 before that date and that we would look at the data," he said when questioned about the possibility of a delay. 

"That is exactly what we are doing, so the roadmap was set up in order to be able to take these sort of changes into account." 

The Telegraph understands the use of face masks, social distancing and advice on working from home are unlikely to be lifted on June 21 amid concern over the Indian variant.

In an article for The Telegraph, health minister Lord Bethell also signalled that twice-weekly tests for children in schools could also continue after the summer.

Mr Hancock’s comments are in contrast to those of Boris Johnson who said last week there was no evidence that definitively suggested the need to delay. 

However, a senior source believed the chance of a postponement had increased. 

The Government has committed to announcing the plans for June 21 on June 14. This week, ministers will receive papers setting out the options from scientific advisors and officials as well as the most up to date data before making a decision. 

Sources said the decision hinged on data on the impact of the Indian variant on hospitalisations, which are largely flat but have increased marginally in some areas.

Covid-19 patients in UK hospitals

"The scientists are more in favour of a two-week extension and that is certainly one of the options that has been put in the papers for ministers," a source said.  

Mr Hancock also declared that the Indian variant was 40 per cent more transmissible than the previously dominant Kent variant – a figure which modelling has previously suggested could overwhelm the NHS if both steps 3 and 4 of the roadmap went ahead.

NHS leaders cast doubt on modelling on Sunday, saying it wouldn’t overwhelm them and that they were "sceptical" about the value of using models which had so often been unreliable. 

However, sources said concerns in Government had been raised by the growth in cases, while Mr Hancock, who appeared on the BBC, said the information on the Indian variant’s rate of transmission made the "calculation" for an unlocking on June 21 "more difficult".

Latest UK cases embed

"In the last week infections have increased significantly, faster than was anticipated," a source said. "Hospitalisations have gone up but not by too much. Everyone is waiting for the figures on deaths. The absence of spikes in the data will give them the confidence to call it."

Lord Bethell said more than 50 million tests have been carried out on schoolchildren since the scheme launched three months ago, and suggested he would like to see the same number deployed again in the coming months. 

"As this virus continues to evolve and attempts to bypass our defences, it is these capabilities that will help us out-manoeuvre the virus in the long term. Fifty million tests have got us here, here’s to 50 million more. Let’s not lose what’s been achieved so far," he said.

Tory MPs reacted angrily to the announcement. Sir Desmond Swayne said ministers were "wasting the advantages afforded by the success of vaccinations".

Figures on Sunday showed daily cases rose 65 per cent in a week to 5,341, although deaths continue to fall and evidence of the efficacy of vaccines mounts.

The vast majority of people in hospital with Covid have either not been inoculated or have had only one jab, indicating the current vaccinations are effective against the variant.

"The link through from the number of cases to the number of hospitalisations is severed but not broken," said Mr Hancock.

"It’s not completely broken but we have made a massive, massive difference."

The Government estimates 60 per cent of the adult population will have been fully vaccinated by June 21, up from the current 52.2 per cent, and jabs are being rolled out for under-30s this week.

Is the UK on track to hit vaccination targets?

But advisers are concerned this may not be enough to stem the spread of the variant.

John Bell, Regius Professor of Medicine at Oxford University and a Government adviser on vaccines, said he would prefer to have 70 per cent fully jabbed rather than 60 per cent before lifting the restrictions.

Although it was for ministers to decide, he told The Telegraph: "Do we really want to blast on the second-last lap or do we want to hang on?"

He also favours continuing with advice to wear masks, socially distance and work from home because the Indian variant is "much more infectious than I thought it was going to be".

Professor Stephen Reicher, a member of the Government’s Scientific Pandemic Insights Group on Behaviours (Spi-B), said there was enough evidence to say that due to the spread of the Indian variant, one of the Government’s four key tests for its roadmap out of lockdown had not been met.

"I think by the Government’s own criteria it’s quite clear that it would be foolish to proceed on the data that we’ve got at the moment. The risk would be very great indeed," he said.

Where is the Indian variant in the UK?

"And of course it’s a balance of risks but I think it would be a major risk to go further in opening up."

He added: "Again, I make the point that it is about data not dates, and if you make it too much about the dates then you box yourself into a corner and I think that’s what the Government has done."

UCL professor Susan Michie, a member of the Government’s Scientific Advisory Group for Emergencies, told The Telegraph: "If the starting point is that we want to avoid a third wave, it would be wise to maintain the restrictions for at least two weeks beyond June 21.

"We have learned from the pandemic that waiting and seeing is too late. One has to anticipate and be ahead of the curve. So we need to learn from our previous mistakes and learn from what other countries have done well."