Customers who hit the "net loss threshold" can be turned into VIP users and are even given incentives like the chance to win FA Cup final tickets, it is alleged.
Once considered VIPs, punters are assigned their own dedicated advisors.
Bet365 staff claim the tactic is "incentivising people to bet". One employee stated: "If they’ve lost, say, US25,000 in that week, then we’ll give them a weekly rebate, normally on a Tuesday, and we’ll give them maybe 10 per cent of that back."
The rebates are all part of the brand's strategy to "reward loyalty".
Though Bet365 users are warned of gambling addiction, the minimum time spent on the site could be as high as eight hours a day.
Junior staff are given free rein to give out US40 cash bonuses and free spins to any punter that rings the firm's customer service line.
A spokesman for Bet365 said: "Bet365 prides itself on providing a safe environment for its customers and goes above and beyond its legal and regulatory requirements to do so, including those set out in the Gambling Commission Licence Conditions and Codes of Practice and we fully refute any allegation or suggestion to the contrary.
"Bet365 is at the forefront of various industry initiatives to further promote and develop, safer gambling practices, including its participation in gambling treatment provider Gamcare’s social responsibility quality trademark scheme, the Safer Gambling Standard.
"As the LCCP makes clear, operators in the gambling industry are entitled to reward their loyal customers provided they do so in a socially responsible way, as Bet365 does.