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 an announce an extension to the lockdown on Thursday.
Sir Keir said Labour would back such a move but the government should be more open about how and when it will end.
The government said talking about an exit before the virus had reached its peak risks confusing the public.
In a letter to Dominic Raab, who is deputising for Prime Minister Boris Johnson while he continues his recovery from coronavirus, Sir Keir offered Labour’s support for an extension.
But he said: “The question for Thursday therefore is no longer about whether the lockdown should be extended, but about what the government’s position is on how and when it can be eased in due course and on what criteria that decision will be taken.”
Millions of people had “played their part” and made sacrifices, he added, 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”.
He urged Mr Raab to commit to setting out the criteria the government will use to inform how and when it intends to ease the lockdown.
And he called on the government to publish an exit strategy now or in the coming week; and to outline the sectors and core public services that are most likely to see restrictions eased.
A government source said: “Our strategy is focused on saving lives. We have been clear that all decisions will be guided by the scientific advice and data.
“Talk of an exit strategy before we have reached the peak risks confusing the critical message that people need to stay at home in order to protect our NHS and save lives.”
The government has previously indicated that work is under way on a plan to lift restrictions, but no details have been published.
Speaking earlier at the Downing Street daily press conference, Chancellor Rishi Sunak insisted the government’s priority would remain saving lives.
And he warned that the government will not be able to protect every UK business and every household during the pandemic but if ministers had not taken the actions they had, “the situation would be much worse”.
NHS England’s Medical Director, Prof Stephen Powis, told the news conference lockdown compliance levels among the public were “very high” and this was beginning to have an impact on hospital admissions,
“We need to keep it that way. We absolutely need to make sure that we keep the benefits of this going forward and we don’t take a foot off the pedal, we don’t become complacent,” he added.
It comes as the Office for Budget Responsibility predicted the UK economy could shrink 35% between April and June, while unemployment surges by more than two million.
But it predicted a sharp bounce back, with GDP likely to jump 25% in the third quarter and a further 20% in the final three months of 2020.
The watchdog based its calculations on a three month lockdown followed by a partial lifting for three months.