Campaigners raise concern over risk of problem gambling as more than 300 24-hour sites spring up

More than 300 slot machine adult gaming centres are running 24 hours a day on Britain’s high streets, despite warnings of the risks they pose to vulnerable gamblers.

Two of the leading slot machine operators – Merkur and Admiral – have opened dozens of new around-the-clock outlets in empty retail units across the country over the last few years. The two firms operate more than 500 venues across Britain, with most now open 24 hours a day.