Online supermarket Ocado has bought 100,000 coronavirus test kits for its delivery staff.
The internet grocery firm has spent £1.5m on the kits and has received 40,000 so far.
It would not say how many of its 30,000 staff had been tested but added it could share kits with the NHS.
Harrow West MP, Gareth Thomas, has called on the government to explain why front line medics are still awaiting tests.
The government says it is ramping up testing, but has only been administering them to about 7,000 people a day.
Labour MP Mr Thomas said it “beggars belief” that routine tests were not being offered to NHS staff.
Ocado said it had purchased the tests to ensure the safety of staff and customers.
It declined to say where it bought them from, how long it took to receive its first deliveries, or to comment on the amount purchased.
The company said demand for its services was 10 times higher than average.
The government has been contacted for further comment.