According to an audit by the commission, the number of problem gamblers aged 11 to 16 has reached 55,000.
It also found 70,000 youngsters were at risk and 450,000 children bet regularly – the equivalent of one in seven children aged 11 to 16.
The audit, reported in the Daily Mail, said the youngsters stake an average of £16 per week on fruit machines, bingo, betting shops and online – all of which are all illegal for under-18s.
The findings were branded “deeply concerning” by the Church of England, which warned the country needs to take the “dangers of gambling seriously”.
The Bishop of St Albans, the Right Reverend Alan Smith, said:”We need to start taking the dangers of gambling seriously – 55,000 children classed as problem gamblers is a generational scandal.”
The Gambling Commission Audit also revealed that children were being inundated with gambling adverts, with two-thirds telling the auditors they had seen it on TV.
It said close to a million young people had been exposed to gambling through “loot boxes” in video games or on smartphone apps.
Loot boxes are chance-based items that can be purchased in video games to win prizes and they have been likened to poker machines.
It also found more children said they had placed a bet in the past week than drank alcohol, smoked or taken drugs.