Labour leader Sir Keir Starmer is urging the government to publish an exit strategy from the coronavirus lockdown this week.
The government is expected to announce on Thursday that social distancing measures will continue.
Sir Keir said Labour would back such a move but to maintain public trust “there needs to be transparency”.
The government said talking about an exit before the virus had reached its peak risks confusing the public.
The Labour leader has written to Dominic Raab, who is deputising for Prime Minister Boris Johnson while he continues his recovery from coronavirus, to say Labour would support a continuation of the measures.
But, he said, the government needed to set out an exit strategy to maintain trust and to ensure that arrangements are in place for it.
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“We’ve got to have the trust of the public,” Sir Keir told BBC Radio 4’s Today programme, adding that it was “inevitable that the lockdown will have to continue”.
“For that trust there needs to be transparency and openness – they need to know what the thinking is on when lockdown will end.”
He said that government planning was previously not quick enough, and said, “let’s not repeat that”.
“Mass testing and then tracing is likely to be amongst the options for ending the lockdown,” Sir Keir said.
“If that is right we need the government to say so because decisions need to be taken now to make sure that the number of tests that are needed and that the arrangements are in place so they can be implemented at the relevant time.”
He said that he believed “in principle” schools should be amongst the first institutions to restart following easing of lockdown measures.
In an interview with BBC Breakfast, however, Sir Keir said it would be “wrong” to put a time on when schools should reopen.
“Until we know the curve is flattening, then I’m afraid we have to stay in the conditions we’re in,” he said.
In his letter to Mr Raab, Sir Keir said millions of people had “played their part” and made sacrifices and “in return, the government needs to be open and transparent with the public about how it believes the lockdown will ease and eventually end”.
Sir Keir warned the “silent pressures” on communities across the UK “cannot be underestimated”, and said that to maintain morale and hope “people need a sense of what comes next”.