The government is looking at "immunity passports" for people who had the disease to be able to escape lockdown. But health experts have warned that it may take 28 days before an immunity test will work and that immunity may not last forever.
It came as Health Secretary Matt Hancock pledged to ramp up the number of tests - to see if people currently have the disease - to 100,000 a day by the end of April.
The government has been on the backfoot over its testing commitments for several days now failing to explain why the UK lags behind its European counterparts - testing just 10,000 a day compared to 70,000 in Germany.