Coronavirus testing for returning holidaymakers has been described as an “absolute mess” after images of overflowing boxes for completed test kits were posted on social media.

Teaching assistant Gavin Marshall captured an image in Sutton, south London, of a drop-off box for testing firm Randox.

Mr Marshall expressed his anger at being “forced to pay Randox over the odds” for a day two PCR test for his daughter, who had recently returned from a holiday in Portugal.

He explained that he drove for half an hour to drop off his sample as there are “so few collection points”, but on arrival found the box “overflowing and insecure”.

The 51-year-old told the PA news agency: “I initially hesitated (and thought) ‘is this ever going to get there’? But the next nearest one was about 45 minutes drive in the wrong direction and I wouldn’t have got there before the deadline.

“So I had absolutely no choice but just to sort of squeeze it in on top of the box and hope for the best.”

Mr Marshall went on: “For many people who might be using that box for their outbound travel, where they’re relying on having a PCR result in order to fly, it doesn’t seem a very secure or guaranteed service that they’ve paid money for.

“The thing that really annoys me is the lack of choice on where to get these tests and who to get them from… in the middle of a pandemic, I would expect much higher levels of professionalism and certainly security.”

He added that the testing system is a “rip-off”.

Tilly Slight, who works in the art sector in London, replied on Twitter to Mr Marshall’s photo with the message “You think that one’s bad?”.

She uploaded an image of a full Randox box with dozens of test kits stacked on top.

Another Twitter user, with the account @tothepoint2019, posted an image of a pair of packed drop boxes.

He described the situation as an “absolute joke”, and claimed the tests “mean nothing apart from ££££ in an MP’s best mate’s pocket”.

He added: “You don’t even have to do the test, just need the reference number for the Passenger Locator Form. Buy the cheapest you can find!”

Paul Charles, chief executive of travel consultancy The PC Agency, said the images demonstrate “the absolute mess that PCR testing has become”.

Mr Charles claimed they are proof that private laboratories “aren’t in any hurry to turn around the results” and warned that personal details and samples are being “left for anyone to take”.

A spokesman for Randox said: “Randox is constantly expanding and improving its Covid-19 testing capacity and associated logistics network, which is already the largest in the United Kingdom, to meet the rapidly growing demand resulting from the loosening of travel restrictions.

“Randox continues to increase the number of drop boxes across the United Kingdom, which already totals over 200, and is increasing the frequency of box collections which are already occurring multiple times per day.

“Randox is providing premium testing services in dynamic and rapidly changing circumstances and is committed to continuously improving its logistics network, to ensure that international travellers receive their results in time.

“All of the sample kits pictured will be processed.”

International travellers entering the UK must pay for a PCR test on or before the second day.

These typically cost around £50, but some are priced at more than £100.

People who are not fully vaccinated must take a second test on or before day eight if they have arrived from an amber list country, or are staying in a quarantine hotel.

This group must also self-isolate at home for 10 days after arrival.

They can leave quarantine early if they receive a negative result from an additional test after at least five days.

But many people have reported delays in receiving pre-ordered test kits, meaning they must stay at home for longer than planned.

Health Secretary Sajid Javid has asked the competition watchdog to investigate the market for travel PCR tests in response to concerns about the cost for families travelling abroad.

In a letter to Competition and Markets Authority chief executive Andrea Coscelli, Mr Javid wrote: “We have all experienced enormous disruption to our lives over this pandemic, but it is not right if some families experience yet further disruption unnecessarily because of potentially unfair practices in the market for private travel tests.

“It is important that the sensible measures we have introduced at the borders are fair and transparent and don’t involve unnecessary costs or low quality provision to people who have made so many sacrifices during this pandemic.”