As many as 4,500 jobs are at risk after bookmaker William Hill announced plans to close 700 branches across the UK.
It said the store closures would begin before the end of the year and come as a result of the government's restrictions on fixed-odds betting machines which came into force in April.
William Hill had the £2 maximum stake on betting machines had significantly impacted that revenue stream. Previously, customers were able to bet up to £100, which was seen as dangerous as it allowed them to lose large amounts of money in very little time.
In a statement, the company said: "The group will look to apply voluntary redundancy and redeployment measures extensively and will be providing support to all colleagues throughout the process."
William Hill is yet to reveal the locations of its store closures, but a report published by the company in March suggested the £2 limit would reduce the company's revenues by £100 million and result in as many as 900 store closures.
Speaking to the BBC, one worker says staff were told about the plans via a pre-recorded conference call. They said: "I thought that was really disrespectful.
"The scale of the closures has come as a massive shock to lots of staff members who had been being assured for months that they would not lose their jobs.
"The upshot is that thousands of people will be left unemployed as a result of this and lives have already begun to be turned upside down."
A spokesperson from the Department for Digital, Culture, Media and Sport said: "By cutting the maximum FOBT stake from £100 a spin to £2, we are helping to stop extreme losses by those who can least afford them.
"The gambling industry has had over a year to make preparations for this change, including to mitigate job losses. We now expect them to provide the right support to any staff affected by planned shop closures."