A tradesman with soaring gambling debts was offered huge credit card increases by the Commonwealth Bank, even after he told the lender about his crippling habit.

David Harris, 30, choked back tears revealing his story at the Royal Commission into the banking sector yesterday.

Mr Harris, from the UK, came to work in Australia in 2013 and found employment as a roofer on a $70,000 salary. At the end of 2014, he applied for his first-ever credit card with CBA on a $10,000 limit.

British tradie David Harris, 30, admitted his gambling problem to Commonwealth Bank after accruing thousands in debt, only to be given a credit card limit increase by the lender. Picture: FSRC. (Supplied)

While he initially paid off the $6000 debt he accumulated on the card, in 2015 he began to use it as a means to gamble – getting to the point where he was consistently maxing it out and making repayments.

While giving evidence to the Royal Commission into Misconduct in the Banking, Superannuation and Financial Services Industry, Mr Harris explained how that decision led to a constant downward spiral.

“I’d max it out, pay off chunks, try and work overtime to try pay off chunks and wait until I got a big win or save up money to pay it off and do it again,” he said.

Ultimately, in a moment of worry after maxing out his $10,000 once again, Mr Harris ordered a second credit card with a $7000 limit from CBA, followed by a third card in November 2015 with an $8000 limit.

An emotional Mr Harris gave evidence against the Bank during the Royal Commission into Misconduct in the Banking, Superannuation and Financial Services Industry yesterday. Picture: FSRC. (Supplied)

Three weeks later the bank offered him a credit limit increase on his initial card from $10,000 to $12,100, which he accepted, before proceeding to accrue enough debt to max out his $27,100 limit.

“It’s a ridiculously large amount of money for someone that was earning my wage, that I do,” Mr Harris said.

“I was working six- and seven-day weeks pretty much for the last three years.

“At one point, I did 62 days in a row, had one day off and then did over 40 days straight - which isn’t easy when you’re working on roofs in the sun.”

Commissioner Kenneth Hayne watched on as Mr Harris explained how Commonwealth Bank continued to offer him higher credit levels, despite him telling the bank that he didn't want to accept any more. Picture: AAP. (AAP)

It was only when CBA offered for him to consolidate his three cards into one with a limit of $32,000 and that he tried changing the address he had listed on his statements.

“The bank proceeded to say that I was eligible for another credit limit increase, to which I replied 'no',” he said.

“They carried on asking what I wanted to do with it, so I explained that I’m a gambler, I have a gambling problem.

“They can clearly see that I’ve got a gambling problem from the transactions that I’ve been making, I don’t understand why they keep offering me more money.”

Commonwealth Bank is one of the financial institutions under the spotlight of the Royal Commission. CBA executive Daniel Huggins gave evidence last week on behalf of the lender. Picture: AAP. (AAP)

Four weeks later, Mr Harris accepted the extra credit limit before it was then increased even more to $35,000.

The 30-year-old attempted to close his account with the bank to prevent himself spending anymore, however after being redirected by both a phone operator and a branch employee, Mr Harris cut up his card.

Despite not accessing the account, which remained open, for three months he eventually ordered a replacement card in a dangerous cycle he told the Royal Commission may have stopped if Commonwealth Bank had heeded his calls for help.

"Two of the hardest things you can do when you’re suffering from any addiction is – one, admit you’ve got a problem, and two, reach out for help and in that phone call to the Commonwealth (Bank), I tried to do both,” he said.

“I tried to reach out for help and I didn’t get any, I got the opposite. I had more credit increases sent through.

“I tried to tell them I had a problem.”

The roofer ultimately came to a negotiation with the bank’s Financial Assistance team that saw him make steady repayments, and he still owes more than $23,000, but said he still receives letters asking him to keep sending money, even if he had been.

Clive van Horen, the executive general manager of retail products at CBA, later told the Royal Commission that the bank still does not have adequate processes in place to deal with customers disclosing issues such as addictions over the phone.