People have struggled to order lateral flow tests online amid a scramble for free kits while they are still available.

The number of free tests available each day will be capped to “manage demand” as the Government scales back free testing for people in England.

Tests ordered online are only available every three days, when previously people could order a new pack every 24 hours.

The public has been encouraged not to stockpile test packs but since the changes were announced the system has been overwhelmed with people trying to order tests.

This could include people who have Covid-19, or those who have been close contacts of confirmed cases.

A message on the Government testing portal states: “Sorry, there are no home delivery slots left for rapid lateral flow tests right now.”

It is not the first time the system has been overwhelmed, with previous issues attributed to delivery constraints.

The UK Health Security Agency said that test availability is refreshed regularly so people are encouraged to re-visit the site every few hours as more will become available.

Ahead of the end of free universal testing in England, it will be necessary for UKHSA to cap the number of tests distributed each day to manage demand

On Monday, Prime Minister Boris Johnson set out his intention to end universal free testing in England, saying that the system had cost more than £2 billion in January alone.

He said that free testing for the general public would end on April 1, but tests would still be available to symptomatic elderly and vulnerable people.

The Living with Covid plan states: “Over two billion lateral flow tests have been provided across the UK since 2020.

“UKHSA continues to have good stock levels and will manage these to provide flexibility in future.

“Ahead of the end of free universal testing in England, it will be necessary for UKHSA to cap the number of tests distributed each day to manage demand.

“Given that advice to test has and continues to reduce, the Government urges people only to order what they need.”

Mr Johnson added: “We’re working with retailers to ensure that everyone who wants to can buy a test.”

But he has faced backlash over the plans and tens of thousands of people have signed a petition on Change.Org calling for tests to remain free and self-isolation to continue.

The costs of tests can vary significantly – one Government supplier charges £5 for a single test but this can reduce in price with bulk buying.

Boots announced it will begin to sell lateral flow tests for people without symptoms.

The health chain said customers will be able to purchase a pack of four lateral flow tests for £17, or one test for £5.99, from boots.com or in stores from Wednesday.

Meanwhile concerns have been raised that NHS staff may not be able to access free tests.

Matthew Taylor, chief executive of the NHS Confederation, said on Monday: “Of particular concern is the Government’s decision to exclude NHS staff from access to free testing from April – 94% of health leaders we surveyed recently said access to free tests for NHS staff and other key workers should not end.

“Patients, staff and visitors deserve to feel confident that they can access and work in services without risking their own health or causing worry to those around them.

“This is particularly true for people from clinically vulnerable groups who may already feel sidelined.

“We urge the Government to reconsider its plan with dedicated funding for continued access to Covid tests for all NHS workers in patient-facing roles.”

Health Secretary Sajid Javid said: “If NHS staff need tests they will be provided with free tests – that will be a decision for the NHS.

“Even before Covid, the NHS has always sensibly made a decision on tests and keeping their staff safe, because keeping staff safe means keeping their patients safe and it’s always about patient safety.”