Bookmakers, online casinos and slot machine companies spent the sum through a mixture of print and digital promotions, as well as affiliate programmes, where third parties are paid to steer gamblers towards particular operators in return for a fee.

The figure, produced by the leading media insights group WARC, far outstrips the £1.2bn that the Treasury collected last year from online casino companies.

Media industry sources said the total spent on gambling advertising is likely to be hundreds of millions of pounds higher because it is difficult to accurately measure the actual amount of digital marketing spend.

That means that the true figure could be close to, or even higher than, the £2.5bn raised last year by the three main duties that the industry pays, which also include taxes levied on slot machines and sports bets.

The chancellor, Rachel Reeves, is under pressure from thinktanks, MPs and former prime minister Gordon Brown to raise these duties at Wednesday’s budget, as she attempts to raise funds to shore up the ailing public finances.

The Betting and Gaming Council (BGC), an industry group that has lobbied hard against any such move, disputed WARC’s estimate, claiming that industry ad spend was closer to £1bn.

This estimate is significantly less than a 2018 figure of £1.5bn given by Regulus Partners, a consultancy favoured by the gambling industry.

As Reeves considers whether to raise gambling duties – and by how much – the higher estimate fuelled calls to ignore industry warnings about the potential impact of a tax rise.

Meg Hillier, the chair of the influential Treasury select committee, said the industry’s spending undermined claims made by its lobbyists, in an occasionally tense evidence session with her committee, that tax rises could have devastating consequences for jobs and growth.

She said: “Unfortunately, the fact that we are told the existence of gambling firms is on a financial knife-edge while they simultaneously plough billions into advertising does not come as a surprise.

“During our session with the BGC, we were warned that any increase in gambling taxation could lead to 40,000 job losses.

“It’s important that the government does not cave into this industry scaremongering.”

Alex Ballinger, a Labour MP who has campaigned for tougher regulation and taxation of gambling companies, said the £2bn figure was an “astronomic sum”.

“Perhaps gambling firms should think about cutting back on adverts that nobody wants to see before pushing back against paying fair taxes on their vast profits particularly given the harms they cause,” he said.

However, leading gambling industry analyst Alun Bowden, of Eilers & Krejcik Gaming, said that any reduction in advertising spend might have unintended consequences, helping illicit operators to gain more of a foothold in the UK market.

“Marketing spend is the main way to mitigate costs and would be the first thing to be cut [if taxes rise], but there is a reason for marketing spend in the first place,” he said.

“If you reduce advertising spend significantly then you give more parity to black market operators who are increasingly spending more on SEO [search engine optimistation], affiliates, streamers and social media.”

James McDonald, the director of intelligence at WARC, said: “The gambling sector has grown to become a significant force in the advertising market, spending more than industry stalwarts such as automotive and cosmetics in recent years.”

“While TV spend is a major focus, social media platforms are also core to the sector’s marketing strategy.”

Will Prochaska, the director of the Coalition to End Gambling Ads, said: “One would think that if the sector is asked to pay a bit more tax in the upcoming budget that they could cut back on their ad-spend rather than lay off all their employees in betting shops, or further reduce what they payout to customers, but that’s a choice for them.”

A BGC spokesperson said: “These claims are misleading as the betting and gaming industry spend on advertising, excluding lotteries, is around £1bn, and has actually declined over recent years.

“Crucially, 20% of all broadcast and digital advertising is dedicated entirely to safer gambling messaging, a voluntary commitment made by the UK industry.

“Further tax rises would simply drive more consumers towards the growing black market that offers no age checks, no safer gambling tools and no tax contribution, while undermining advertising spend that differentiates the regulated market that supports over 11,000 jobs, contributes £506m to the UK economy, and provides £138m a year to British sport through sponsorship.”