The owners of gambling website BetCity have been fined €2.65 million after a 21-year-old gambler lost €45,000 in two weeks.

The Dutch gambling regulator Kansspelautoriteit (Ksa) said Betent had failed to protect the man when he signed up for the site and intervened far too late when he started racking up debts.

By the time the site’s administrators stepped in, cutting the player’s maximum stake from €100,000 to €400, he had already placed €64,000 in bets.

Betcity’s safeguards – an email advising players to set a lower limit when they sign up and a link to a page about responsible gambling – were not rigorous enough, the regulator said.

The Ksa said it was not an isolated incident. The regulator studied 10 cases of players aged between 18 and 23 who had lost €500,000 between them in a short time and found Betcity had breached the rules in each case.

“We have a licensed gaming market based on the idea that people who want to gamble can do so safely,” Michel Groothuizen, chair of the Ksa’s board, said.

“Providers have a duty of care towards their players and must respond adequately to excessive playing. Heavy losses are an important indication of that.”

Bettent did not respond to requests from NOS for comment, but the company is expected to challenge the decision in court.

Two years ago Betcity was fined €3 million by the regulator for failing to take action against suspected money laundering.