JP Morgan Chase signalled today that City firms are preparing to make huge bonus payments after it kicked off the US bank reporting season by smashing profit expectations.

The bank revealed it had set aside $7.3bn (£4.6bn) in the third quarter to pay staff, taking the total remuneration pot for the first nine months of the year to $21bn, 23% more than at the same time last year.

The admission by JP Morgan Chase that it was preparing to raise bonuses came as Goldman Sachs was expected to report that it too was enjoying a bumper year and its bonus pool could reach $22bn.

Mounting expectations that bankers are looking forward to huge pay cheques barely a year after the banking system was bailed out by governments across the world have forced the biggest payers in the City to capitulate to government demands to adopt the G20 principles on pay.

After a meeting with City minister Lord Myners in the Treasury a dozen international banks agreed to support the reforms to pay structures that would require bonuses to be spread over three years and clawed back if profitable deals turned sour later.

Three European banks which are not regulated directly by the Financial Services Authority but which have large City operations – BNP Paribas, Deutsche Bank and Société Générale – also agreed to sign up to the principles.

The banks, which included Goldman Sachs, JP Morgan and Bank of America Merrill Lynch, issued a joint statement in which they pledged to "work with the FSA and regulators in our home countries in adopting the reforms, recognising that all G20 nations have also committed to their implementation to ensure a level playing field".

But this does not mean that the banks will cap the size of payouts. The figures from JP Morgan showed that the bonus pool from which staff would be paid was being hugely inflated by revenues from the bond markets, spurred by the need of governments to pay for bank bailouts.

Research by the Wall Street Journal showed that employees at JP Morgan were expected to earn an average of $133,971 this year. At Goldman Sachs the estimate is even higher, with average pay expected to be $743,112.

Jamie Dimon, chief executive of JP Morgan, insisted that the bank's guidelines already followed the G20 strictures. "We're committed to treating each individual properly," said Dimon.

The prospect of big financial services payouts has infuriated unions. Speaking at a London conference on private equity today TUC leader Brendan Barber said: "I would question the 2% management fee and 20% cut of profits that has allowed an elite in the industry to do very well.

"There is also a question of tax. It was one of private equity's senior figures who said he paid less tax than his cleaner. It is still the case that private equity people pay capital gains and that represents less tax than a cleaner pays.

"This is not just about the industry improving its public relations. It is also about substance and how much the industry has really changed."

JP Morgan was the first of four major US banks to report third-quarter figures this week. Goldman and Citi report on Thursday and Bank of America Merrill Lynch on Friday. JP Morgan's net profits of $0.82 a share in the three months to 30 September were much greater than Wall Street's expectations of $0.49-$0.51.

Dimon credited "broad-based growth" across JP Morgan's investment banking, asset management, commercial banking and retail banking operations. But he also warned that consumers were finding it increasingly hard to repay loans, particularly on credit cards, where the bank expected to lose "a lot of money".

"While we are seeing some initial signs of consumer credit stability, we are not yet certain that this trend will continue," said Dimon, who repaid government bailout money three months ago.

JP Morgan set aside another $2bn to cover future losses on personal loans. Provisions for credit card losses grew to $5bn, more than double the amount put aside a year ago. Its retail banking arm made a bad-debt provision of almost $4bn to cover consumer loans that turn sour, up from $3.85bn three months ago.

The overall strong performance was partly due to a $400m "write-up" on the value of JP Morgan's legacy leveraged lending and mortgage-related assets.

JP Morgan's investment banking arm made net profits of $1.92bn, while commercial banking made $341m. However, the large provisions against credit losses meant that retail banking made a net profit of just $7m, while the credit card arm lost $700m.