Gambling companies are on high alert ahead of the expected publication of a long-awaited White Paper next week.

Sources told The Mail on Sunday that the wide-ranging review of the industry – expected to be 200 pages long – will be released within days. The document will lay out new rules and guidance for the controversial sector.

The review was initially due to be published two years ago, but investors and gambling companies have been left in limbo amid delays.

It is expected to introduce a flurry of restrictions on online gambling, including a potential cap on online slot game stakes to between £2 and £15, with a £2 limit for under-25s.

Around 300,000 people are dubbed ‘problem’ gamblers in the UK, with campaign groups pushing for tighter measures to protect them.

Shake-up: The review was initially due to be published two years ago, but investors and gambling companies have been left in limbo amid delays

The shake-up is also set to introduce new controls around free bets, hoping to crack down on features that can push players towards developing an addiction. This would be a blow for gambling companies, whose revenues are bolstered by high-spending customers.

Gambling firms could be boosted by the scrapping of restrictions placed on bingo halls and casinos where regulation has not been reviewed since 2005. Part of this will be providing consistent rules about slot machines.

Shares in the likes of Grosvenor Casinos owner Rank Group are likely to be lifted as a result of these potential changes.

A spokesman for the Department for Culture, Media and Sport, said: ‘We’re determined to protect those at risk of gambling-related harm.’