The Christian Centre for Gambling Rehabilitation (CCGR) was speaking after former betting staff claimed their company Coral prompted them to give them free drinks, bets and even lunches to keep players on the machines.
Its investigation also found betting shops got bonuses if a certain amount of money was made on the fixed-odds betting terminals (FOBTs).
Players can lose hundreds of pounds in minutes on FOBTs, which have a predetermined success rate for players - unlike other forms of betting.
Speaking on Premier's News Hour Peter Chan, from CCGR, said: "Commercially speaking it's difficult to stop the bookies from encouraging their customers.
"A hundred pounds per spin is too much - way too much.
"I would still advocate for reducing the stake to a maximum of twenty pounds."
Commenting on the likelihood of a change in the law, Peter Chan added: "They [betting shops] earn their money from these FOBT machines mainly nowadays, so I don't think the government would like to do that because they get a lot of tax from them.
"A compromise is to reduce the stake."
Coral told the BBC in a statement: "Recent health surveys show that problem gambling rates have in fact fallen since the introduction of FOBTs and the average Coral customer's loss per session on a FOBT is around £6-9.
"The introduction of supervised stakes above £50 from April last year has had a profound change in customer behaviour, with an approximate 70% reduction in stakes above that level.
"Training, tools and processes are in place throughout the business to ensure that potential problem gamblers are identified and protected."
