The length of the lockdown is not "absolutely fixed" a Cabinet minister has warned, as Boris Johnson said the Government "will not hesitate to go further" with measures aimed at limiting the outbreak.
Speaking to Sky News, Cabinet minister Michael Gove said the length of lockdown restrictions "depends on all of our behaviour".
The Chancellor of the Duchy of Lancaster warned that ministers would not hesitate to enforce tougher rules, but said the evidence is people are obeying them.
Speaking to Sky News, Mr Gove said: "There are different projections as to how long the lockdown might last.
"But it's not the case that the length of the lockdown is something that is absolutely fixed.
"It depends on all of our behaviour. If we follow the guidelines, we can deal more effectively with the spread of the disease."
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Speaking to BBC's Andrew Marr later on Sunday morning, Mr Gove added that the public must prepare for a "significant period" of lockdown.
Not only could the lockdown period lengthen, the conditions of it could become stricter in a bid to keep the number of deaths and cases in the UK as low as possible, Mr Johnson said in his letter to all households.
"We will not hesitate to go further if that is what the scientific and medical advice tells us we must do," the Prime Minister wrote.
"We know things will get worse before they get better.
"But we are making the right preparations, and the more we all follow the rules, the fewer lives will be lost and the sooner life can return to normal."
The total number of virus-related deaths in the UK now stands at 1,228.
Professor Stephen Powis, National Medical Director of NHS England, has warned that keeping UK coronavirus deaths below 20,000 would be "a good result".
Speaking to Sky News, Mr Gove said the Government is "very concerned" by the increase in the number of deaths from coronavirus.
"It's absolutely critical that all of us stay at home, that we limit our trips away from home to just one a day for exercise, we limit the amount that we shop."
Mr Gove added: "If we do that, we can all play our part in helping the NHS."
Mr Gove said the Prime Minister remained "very firmly in charge" and would hold another meeting by video conference on Sunday.
He also confirmed that Foreign Secretary Dominic Raab is the "designated deputy" should Mr Johnson's condition worsen and he could no longer govern.
Asked if the Government had been observing its own coronavirus guidance after ministers developed symptoms, Mr Gove told the BBC's Andrew Marr:
"We've been doing everything we can to observe that advice and it's certainly the case that within the House of Commons people were seeking to maintain an appropriate distance from one another."
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