Keir Starmer has been urged to honour his pledge to ban ticket touting, amid fears that the policy will be left out of next month’s king’s speech, potentially costing fans “hundreds of millions”.

Music industry groups called on the prime minister to act as fresh evidence showed that professional ticket “traders” had targeted BBC Radio 1’s Big Weekend next month, making huge mark-ups through sites such as Viagogo and StubHub.

Starmer said in November that the government would “stop fans from being ripped off” by making good on Labour’s 2024 election manifesto promise to outlaw resale of tickets for profit.

A host of globally renowned artists have backed the plan, including Radiohead, Dua Lipa and Coldplay.

But in a meeting in parliament last week, the minister responsible for the policy, Ian Murray, told music industry groups not to worry if the measure was not part of the king’s speech on 13 May, which sets out the government’s upcoming policy slate.

Murray referred to other potential legislative avenues such as private members’ bills, widely seen as an unreliable means of turning policy into law.

The apparent hint at delay has prompted dismay among music industry groups, the chair of the culture select committee and the consumer organisation Which?

The telecoms company and venue sponsor O2 estimates that fans have lost £60m to touts since the policy was announced, with fans of acts including Olivia Dean, Bad Bunny and Ariana Grande being “fleeced” by mark-ups of up to 1,000%.

They voiced their concerns as evidence showed that ticket touts were making huge sums from the Radio 1 Big Weekend event in Sunderland, despite measures by the BBC and the official seller, Ticketmaster, to keep prices low and ensure priority access for local people.

Although there was a two-ticket limit for buyers, some touts were advertising up to 30 in a single Viagogo listing, according to evidence gathered by the music industry group FanFair Alliance and shared with the Guardian.

On 12 March, 449 tickets for Big Weekend were listed between Viagogo and StubHub, all over the “face value” price. The most expensive was £622 for a £45 ticket.

By 31 March, the number of tickets across the two sites had increased to 571 excluding duplicates. They were advertised for a combined price of £86,546, compared with their face value of £27,278.

Despite 90% of tickets being reserved for local people, tickets were listed by touts in the Netherlands, Dubai, Hong Kong, Belgium, Israel, North America, Sweden, Slovakia, France, Ireland and Singapore, often without traders’ details, an apparent breach of regulations designed to protect consumers.

In some cases, terms and conditions that mean fans could be turned away if they bought from a tout, were not disclosed. StubHub said it had failed to flag up resale restrictions on Big Weekend in error and had “updated this accordingly”.

“If it is not in the king’s speech it would call into question whether the government is serious about protecting music lovers, and everyone who enjoys live events, from being ripped off,” said Caroline Dinenage, who chairs the culture select committee, which has produced a “fan-led” review of live music.

Lisa Webb, consumer law expert at Which?, said: “The government has promised to put fans first, but if this legislation is not included in the king’s speech, the only ones celebrating will be the rip-off secondary ticketing websites and online touts.”

Annabella Coldrick, chief executive of the Music Managers Forum, said: “A ban on ticket touting was one of only two music-related commitments in the Labour manifesto, alongside fixing EU touring.

“These are widely supported, pro-growth measures that will deliver tangible benefits to the British public.” She said any further delay would “continue to cost […] constituents hundreds of millions of pounds a year”.

StubHub said people selling tickets through the site must comply with its requirements, including a rule that touts must provide clear address details.

“Independent analysis shows that price caps on ticket resales push fans towards unsafe alternatives where the risk of fraud is significantly higher,” the company added.

Viagogo said it was a “regulated marketplace, in full compliance in the UK and all markets where we operate, with robust security and fraud measures in place.

“Sellers on Viagogo must adhere to strict policies. If we believe or become aware of any activity being unlawful or in breach of our user agreement, we will suspend or ultimately terminate their account and listings.”

The government has been approached for comment.