Some passengers arriving in the UK are having to extend their quarantine or pay for additional Covid-19 tests as private labs are failing to deliver results on time, Which? has found.

The news raises concerns about the capacity of the travel testing system weeks before international travel is set to re-open.

Currently, anyone arriving in the UK (unless exempt) must quarantine for a mandatory ten days and take a PCR test on day two and day eight of their quarantine.

These tests typically cost between £160 and £200, but can cost over £500.

Travellers must receive negative results for both tests to leave quarantine after day ten.

However, social media and review sites have been flooded with complaints about test result delays, with a Facebook group for people suffering problems with the system amassing around 1,500 members, and Which? has also heard from travellers who did not receive their test results within ten days.

Without test results, travellers face having to pay hundreds of pounds for additional tests or stay in quarantine for longer than they need to, potentially causing problems for those who cannot work from home.

The consumer organisation also understands that at present, only four private test providers out of more than 500 on the government’s list of providers have been accredited – Nationwide Pathology, Source Bioscience, Oncologica and Eurofins Forensic Services.

Of those four, only Nationwide Pathology and Oncologica offer day two and day eight test kits, raising concerns about oversight of the test providers.

With mass travel set to resume next month, Which? is concerned that the travel test system – which is already struggling to handle demand when international travel is restricted – is at risk of being overwhelmed, and potentially collapsing when restrictions are lifted.

Rory Boland, Which? Travel editor, said: “The UK’s travel testing system can’t cope with demand, even when relatively small numbers of people are travelling.

“It’s clear the system could buckle under the pressure when mass international travel restarts and hundreds of thousands more people are reliant on it.

“Travellers shouldn’t have to shop around for something as crucial as a test provider – they simply need a service that is accessible, reliable, and delivered on time.

“It is critical that the government addresses issues with testing ahead of restarting international travel, and ensure that travellers are not left to the mercy of poor-quality providers or unreliable services when trying to do the right thing in following government requirements to travel safely.”

Which? is urging the government to urgently address the problems currently affecting the PCR testing market with regard to availability of information, accreditation, pricing and accessibility of tests, as well as the poor quality of service by some providers.

It must also ensure there are effective consumer protections in place for travellers in the event of any problems with testing, ahead of reopening travel after May 17th.

In a statement, the department of health and social care said: “We are carefully monitoring issues raised by the public, raising every complaint with private test providers.

“We also monitor all providers’ performance, including their delivery and test turnaround times.

“We will take rapid action against any company that is providing an inadequate service.

“In the first instance, they will receive a warning and are given five days to demonstrate they have addressed concerns, and if not, they are removed from the gov.uk list.”