The UK faces a "tipping point" where "more restrictive measures" could be brought in to slow the spread of coronavirus, the health secretary said.

Matt Hancock said "people have got more relaxed over the summer" but "now is the moment when everybody needs to get back" to following the rules.

He told Sophy Ridge On Sunday he was "worried" too many people are breaching self-isolation guidance, leading to the government making it illegal in England.

Discussions are underway today on potential lockdown measures in London, Mr Hancock revealed.

#Marr: What is the current #Covid_19 alert level?

Health Secretary Matt Hancock: "We’re currently at level three but obviously the clinicians look at this all the time"https://t.co/kcSihTH4s2 pic.twitter.com/9JXQv1JP4Y

— BBC Politics (@BBCPolitics) September 20, 2020

He also refused to rule out "national action" when pressed on the possibility of a second national lockdown.

And Mr Hancock made clear people should report on their neighbours for breaking any of the emergency Covid-19 laws.

Asked if he would, the cabinet minister said: "Yes - and everybody should... Everybody has got a part to play in this."

It comes as daily new coronavirus infection figures shot up to a level not seen in more than four months, with 4,422 reported on Saturday and 4,322 on Friday - the highest since 8 May.

We all face a choice.

If everyone follows the rules, then we can avoid a further lockdown. pic.twitter.com/MOKw8UXQLv

— Matt Hancock (@MattHancock) September 20, 2020

The government's chief medical and scientific advisers, Prof Chris Whitty and Sir Patrick Vallance are expected to step in on Monday to reveal their latest advice on countering the growth of the pandemic.

Earlier, Labour leader Sir Keir Starmer said ministers had "lost control of the testing system".

He told Sophy Ridge: "If I was the prime minister, I would apologise for the fact that testing is all over the place and instead of using the summer to prepare for the autumn, which is what we said should happen, we're in this position just when we need testing to be at its very best, it's near collapse."

Some people in Covid-19 hotspots have complained they cannot book a test or are being sent hundreds of miles away to get one.

Dido Harding, head of Test and Trace, said earlier this week no-one could have foreseen the big rise in demand that coincided with most schools fully reopening.

She was backed by Mr Hancock, who said on Sunday: "We expected an increase in demand due to people with symptoms.

"What nobody could have predicted is that a whole load of people who don't have symptoms suddenly came forward for a test."

But the government was urged by Professor Carl Heneghan, of the Centre for Evidence-based Medicine at Oxford University, not to introduce new restrictions too quickly.

"As we look at the data, COVID is operating in a seasonal way," he told Sophy Ridge. "So what we have to do now is slow down. This is a long winter.

"We cannot afford to go now with harsh measures because the impact on the economy here is going to be significant...

"If we go now it is too early."