Food delivery company Ocado has said its decision to order 100,000 Covid-19 testing kits for staff would help keep grocery supplies flowing and protect both staff and the public - but has promised to hand them over to the NHS if required.

The firm said it wanted all its staff to be tested regularly to ensure customers who cannot visit the shops because they are observing lockdown protocols can receive deliveries safely.

It has paid £1.5m for the testing kits, with 40,000 already delivered and a further 60,000 to come. Ocado refused to state from which company it had bought the tests.

While Ocado has managed to source testing kits for staff contributing to the food supply effort, nurses and doctors have been left waiting.

A spokesperson for Waitrose said the supermarket had no plans to order kits but it had put in place measures to protect both staff and customers, while Morrisons said it was “open-minded” on testing and was waiting for a government-approved plan. Sainsbury’s and Tesco did not immediately respond to requests for comment.

Ocado said testing would help ensure staff can continue “working round the clock” to get as much food delivered to as many homes as possible, with demand 10 times higher than average.

Its ordering service has buckled under the strain of rocketing orders, prompting its chairman, Stuart Rose, to urge Britons to stop stockpiling groceries, insisting “nobody will starve” during the coronavirus outbreak.

“No matter how hard we work, we do not have enough capacity to serve these unprecedented levels of demand,” Ocado said in an emailed statement.

“Our priorities are the safety and wellbeing of our customers, colleagues and the community.”

The kits will allow Ocado to test grocery packers and delivery drivers who have emerged as one of the most vital segments of the workforce during the coronavirus crisis because of their role in bringing food to those who cannot leave the house.

Anyone involved in the production, processing, distribution, sale and delivery of food has been given “key worker” status, affording them certain privileges such as permission to send their children to school.

Ocado said if it were asked to do so, it would hand over testing kits to the government to ensure that health workers were first in line.

“Ocado is clear that the NHS takes priority in the national effort to combat coronavirus and kits will be made available to the NHS if and where required,” it said.

The government has said that tests for NHS healthcare workers will be rolled out next week, allowing them to confirm whether they have been infected or are safe to work.

It bought 3.5m of the kits but has been criticised over the time it has taken for them to reach frontline staff most at risk of contracting the virus from patients.

While key workers have had to wait to be tested, private health firms have come under fire for selling thousands of test kits to wealthy buyers for up to £295 each.

Public Health England said last week that mass home-testing would be possible “within days” via a procedure that involves pricking the finger to produce a drop of blood, which is then analysed by a device. The test is being validated in Oxford to ensure it works.

The health body said the kits would soon be available on the high street, or to order via Amazon’s delivery service.

But Prof Chris Whitty, the government’s chief medical adviser, later played down the idea that millions of the tests would be available on the internet this week.

High street pharmacist Boots said on Friday night that it had agreed to help the government open drive-through Covid-19 testing facilities by assisting with recruitment of staff, although it has no plans to test in stores.