A new NHS Test and Trace system will officially launched across England tomorrow, with 25,000 contact tracers aiming to cut off routes for Covid-19 to spread and control local flare-ups by "hunting down the virus."

But plans for local lockdowns have been described as a "recipe for chaos" by some, and other key medical figures have been critical of the Government's handling of this "dangerous phase" of the country's Covid-19 response.

Unveiling the mass contact tracing system, health secretary Matt Hancock has urged the public to carry out their "civic duty" and make it work, with the only other option being to continue with lockdown.

People with coronavirus will have their contacts traced under the scheme, and testing facilities or enforced local lockdowns may be quickly deployed if there is a local outbreak.

Under the plans, anyone with coronavirus symptoms will immediately self-isolate and book a test, preferably at a testing centre or, if necessary, for delivery to their home. Their household should start a 14-day isolation period too.

Testing facilities are currently up and running across south London, and with lockdown becoming increasingly hard to enforce, especially in London parks and green spaces, the Government is keen to move forward with the next phase of testing.

Mr Hancock told the daily press briefing: "The big question that we're all working to answer is this: until an effective treatment or vaccine comes through how can we get back to doing more of the things that make life worth living without risking safety or putting lives at risk?

"NHS Test and Trace is a big part - not the only part - but a big part of the answer to that question."

Mr Hancock said that by tracking infected people and isolating their contacts, and by continuing social distancing, the national lockdown could be replaced with individual isolation.

"This is national effort and we all have a role", he added.

"The virus exists only to reproduce - that's its sole biological purpose, to make as many copies of itself as possible.

"If we can thwart that purpose, we can control the virus and ultimately defeat it.

"We must all follow the NHS test and trace instructions as this is how we control the virus, protect the NHS and save lives."

The chief executive of NHS Providers, Chris Hopson welcomed the new programme but said speeding up test results was key and that local plans had only just started.

He warned that the infrastructure needed to roll out a "world-class" test, track and trace system will not be in place by June 1 ahead of a partial relaxation of lockdown restrictions in England.

Andy Burnham, Mayor of Greater Manchester, went further, saying the strategy could be a "recipe for chaos" and Boris Johnson's Government needs to "regain a grip" on the crisis and focus instead on strengthening a tracking and tracing system.

Baroness Dido Harding, executive chairwoman of NHS Test and Trace, said the scheme was central to easing the lockdown further.

She said: "NHS test and trace is designed to enable the vast majority of us to be able to get on with our lives in a much more normal way, but it requires all of us to do our civic duty.

"We will be trading national lockdown for individual isolation if we have symptoms.

"Instead of 60 million people being in national lockdown, a much smaller number of us will be told we need to stay at home, either for seven days if we are ill or 14 days if we have been in close contact."

Earlier, Prime Minister Boris Johnson suggested the new plan would not reach the "world-beating level" he promised by June 1, but would take a few weeks.

He also committed to ensuring test results are returned to individuals within 24 hours - but refused to give a target deadline.