Online casinos will face tougher restrictions under government proposals to overhaul Britain’s gambling laws but the majority of measures will be subject to further consultation, signalling even more delay to long-awaited changes.

A white paper, the result of a review launched in 2020, is due to be published on Thursday, after being postponed multiple times.

Ministers will unveil plans intended to make gambling safer, following a string of high-profile cases where customers have suffered huge losses or taken their own lives.

Concrete measures expected in the white paper include:

• A 1% mandatory levy on industry revenues

• Online slot machine stakes limited to between £2 and £15

• Measures to slow down online casino games

• Looser restrictions for land-based casinos

• Government-run safer gambling campaigns

Some of the most hotly contested measures, including affordability checks for punters making big losses, curbs on digital marketing and the exact level of stake limits of online slot machines, are expected to go out for further consultation, amid a legislative backlog in parliament.

Iain Duncan Smith, the former Tory leader who chairs a cross-party parliamentary group examining gambling harms, told the Guardian he was concerned about the white paper, warning that putting out so many measures to consultation was “tantamount to doing nothing”.

It is understood there has been no decision on limits for stakes on online slot machines games, which are currently unlimited despite carrying some of the highest rates of addiction of any gambling product.

The consultation is likely to propose limits of £2 for under-25s, in line with the cap for customers of all ages on shop-based fixed-odds betting terminals (FOBTs). Older players may be allowed to bet up to £15 per spin but the exact levels will be decided at a later date.

On affordability checks, which campaigners say could stop people suffering financial ruin, the government is understood to be leaning towards a light-touch option, which would see firms perform credit checks when customers lose a certain amount.

Lobbyists for the £11bn-a-year industry have campaigned hard against tougher checks that would require operators to demand proof of earnings.

However, ministers are expected to ask the Gambling Commission, the industry regulator, to consult on when to perform such checks. An early draft of the white paper envisaged doing so for punters who lose £1,000 in a day or £2,000 over 90 days.

Curbs on digital marketing, such as promotions sent to customers offering “free” bets or bonuses, are also set to go to further consultation.

Two sources with knowledge of the discussions said a “legislative backlog” in parliament, partly due to measures required as a result of Brexit, made it impossible to introduce new curbs on marketing without a potentially lengthy consultation process. Advertising is not expected to face any new restrictions in the white paper.

In a letter to fellow ministers, the culture secretary, Lucy Frazer, said any drop in industry revenue as a result of the measures “will be the foregone income from people gambling unaffordably,” the Times reported.

As expected, the industry will be subjected to a new mandatory 1% on its “gross gaming yield”, effectively revenue, to fund addiction education, treatment and research.

A 1% levy would have raised more than £100m in each of the three years before the pandemic crimped the industry’s income.

The gambling sector currently makes voluntary contributions that vary depending on the company.

The Department of Health is also expected to take responsibility for safer gambling messages, which are currently overseen by the industry itself and the GambleAware charity.

While ministers hope to impose tougher curbs on online gambling, land-based casinos will see regulation loosened.