Documents mistakenly published online on Tuesday showed Lisa Nandy, the Culture Secretary, has drawn up plans to raise licence fees for gambling companies by as much as 30%.

In an embarrassing gaffe, the Department for Digital, Culture, Media and Sport (DCMS) briefly published a consultation on proposed increases to fees charged by the Gambling Commission.

The regulator has proposed a 30% rise while the Government wants a 30% increase with 10% of that ring-fenced for tackling the black market. A third option under consideration is a 20pc increase.

Currently, the Gambling Commission collects £26.3 million in fees each year. A 30% increase would push this figure to just under £35 million.

These proposals follow Labour’s recent tax changes, which the industry claims could threaten up to 40,000 jobs.

Major gambling firms anticipate losses in the hundreds of millions, with executives warning that higher costs could drive billions of pounds into the untaxed black market.