The ticket resale website StubHub may have failed to prevent breaches of consumer law on its platform when it allowed a prolific tout to advertise more than 300 tickets for a Lewis Capaldi concert, experts have said.

StubHub and fellow secondary ticketing platform Viagogo are under intense scrutiny from ministers, who are considering whether to ban for-profit ticket resale in an effort to protect fans.

Despite the increased attention, analysis of listings on StubHub indicates the use of business practices that consumer groups and music industry figures and ticketing experts believe are likely to be unlawful.

One company, TG Cyprus Event Services Ltd (TGCES), was listing tickets for Oasis, Billie Eilish, the England v India cricket Test series and autumn rugby internationals, as of early July.

TGCES, whose name StubHub is required to disclose because the company sells more than 100 tickets a year, also advertised Wimbledon final seats for £41,900 each.

But the event that appears to have been most heavily targeted by TGCES was the opening night of a hotly anticipated series of arena shows by Capaldi.

The tour, the singer-songwriter’s first after a two-year period in which he has struggled with his mental health, sold out within seconds. Disappointed fans expressed their outrage when resale sites including Viagogo and StubHub began advertising tickets at large markups soon afterwards.

Both companies say they do not set the prices charged by sellers on their platforms and provide guarantees to ensure fans are protected if anything goes wrong.

According to listings analysed by the Guardian, TGCES advertised at least 306 seats for Capaldi’s tour opener at the Sheffield Arena on StubHub on 6 September. The tickets were on sale for up to £248, more than three times their face value.

Ticketing experts questioned whether it was possible for one company to advertise so many tickets without breaking the law.

“These listings give very clear reason to suspect industrial-scale criminality,” said Reg Walker, a ticketing and security expert.

“There is no legal way to harvest tickets in such bulk,” he said, adding that many touts did so by using illegal methods such as automated bots or multiple identities, to bypass purchase limits. “That would be fraud,” Walker said.

StubHub said it did not condone the use of bots but said they were “an issue that takes place on primary platforms” – the authorised tickets sales agents – and said these websites should do more to tackle them.

Walker said the only plausible alternative explanation for TGCES listing so many tickets was that it was engaging in a different, but also fraudulent, practice known as speculative selling.

In the touting world, “spec” selling is when professional ticket traders list and sell tickets that they don’t have. They then try to source a ticket for a lower price elsewhere, leveraging their touting contacts and knowledge of the ticketing market.

If they are successful, they pocket the difference. If they are not, they typically cancel the transaction and process a refund, leaving the buyer disappointed.

The Guardian has previously published evidence that touts have used StubHub and Viagogo to profit from speculative listings. Resale platforms receive a commission on every sale.

StubHub did not address the TGCES listings directly but said it did not permit speculative selling on its platform.

Lisa Webb, a law expert at the consumer group Which?, said the Capaldi listings were “yet another example of a broken ticketing industry that desperately needs fixing”.

“Which? is calling on ministers to urgently put a stop to the touts and introduce a price cap to ensure that tickets can only be resold on secondary sites at the original price paid,” she said.

“Resale platforms must also be forced to verify that the seller owns a ticket before it can be listed on their site.”

Last year, the Guardian revealed that TGCES was advertising 1,596 tickets for the long-anticipated Oasis reunion tour, which proved to be a feeding frenzy for professional touts.

StubHub removed the listings shortly after the Guardian approached the company for comment but appears to have allowed TGCES to return to the platform.

A spokesperson for StubHub said: “We enforce strict measures to protect consumers. Any ticket listings found not to be compliant with our requirements are removed.”

TGCES did not return requests for comment sent to its website and multiple employees on LinkedIn, including a person whose corporate records suggest is the company’s director, Nikolas Karasamanis. It has previously also failed to respond to requests for comment.

A spokesperson for Ticketmaster, one of the primary ticket agents for Capaldi’s tour, said: “Ticketmaster has capped resale prices at face value since 2018. We fully support the government’s plans for an industry-wide cap that would remove the incentive for touts to exploit fans and prevent them from paying inflated prices on unauthorised sites.

“We also urge the government to take further action by cracking down on bots and banning speculative ticket sales.”

Ticketmaster is the subject of a separate investigation by the Competition and Markets Authority over whether it broke consumer law in the way it sold more than 900,000 tickets for Oasis’s reunion tour last year.