Sir Keir Starmer is demanding that Boris Johnson sets out an "exit strategy" from a quarantine regime for international travellers, as Labour indicates that it will not stand in the way of the new rules this week.
The Sunday Telegraph understands that Labour will not attempt to oppose a regulation introducing the 14-day quarantine rules when it is laid in Parliament on Monday - saving the Prime Minister from a potential rebellion by some Conservative MPs who have lined up against the scheme.
But Labour is calling for the Government to spell out how it plans to replace the "blunt tool" of the blanket quarantine with a "more targeted approach".
In a letter to Priti Patel, the Home Secretary, Nick Thomas-Symonds, her Labour opposite number, said any exit strategy should include a 24-hour turnaround on coronavirus tests, a "sector-specific support package" to help airlines and other industries affected by the rules, and details of the Government's plans for so-called "air bridges" between the UK and other countries.
Mr Thomas-Symonds, the shadow home secretary, also called for ministers to publish the full advice provided by the Scientific Advisory Group for Emergencies (Sage) on quarantining travellers from abroad, "to provide transparency on the decision-making process."
In the letter to Ms Patel, seen by this newspaper, he said: "These would be important steps in helping to provide an exit strategy for quarantine restrictions, thus helping address the economic consequences, which are likely to be hugely damaging and potentially costing many thousands of jobs.
"By increasing testing, tracing and isolating capacity, as Labour has already called for, the United Kingdom would be in a far better position to allow those who are quarantining, and who are subsequently identified as not having the virus to re-enter society."
Mr Thomas-Symonds added: "In recent weeks, Virgin Atlantic, Ryanair and British Airways have all announced job cuts ... the Government must act quickly and put in place a support package for the aviation sector."
The intervention comes after more than 20 Tory MPs demanded a rethink of the plans, with many more privately opposed to the scheme.
A poll conducted last week by ORB found that 75 per cent of people continue to support the quarantine policy - although public backing has fallen from 92 per cent at the end of April, when the plans were first disclosed by The Sunday Telegraph.
The scheme will be laid before Parliament tomorrow as a statutory instrument (SI) which does not automatically go to a vote.
The Sunday Telegraph understands that Labour has decided not to attempt to formally oppose the measure by tabling a motion to annul the SI.
But Mr Thomas-Symonds said: “The Government has had months to develop a more effective approach that can help protect the public’s health and the health of the economy."
Defending the scheme last week, Mr Johnson said: "As we get the rate of infection down, with the efforts that we are making as a country, it is vital that we avoid reinfection from elsewhere."
Willie Walsh, chief executive of British Airways’ parent company IAG, told Sky News that the incoming quarantine rule “has in effect torpedoed our opportunity to get flying in July”.
The firm has been considering legal action.
On Friday, Brandon Lewis, the Northern Ireland Secretary, said alternatives to the quarantine scheme were currently being worked on.