The financial ombudsman handled a record 11,000 complaints a week about payment protection insurance (PPI) mis-selling in the last three months of 2012.
This was around double the rate for July to September and highlights the "volatility" of cases, a spokesman for the Financial Ombudsman Service (FOS) said.
The FOS received just under 245,000 PPI complaints in the first three quarters of the financial year 2012/13 - compared with around 158,000 cases in the whole of 2011/12.
The FOS spokesman said that this year so far it is taking on between 8,000 and 10,000 new PPI complaints each week, meaning it is on course to receive more than 350,000 this financial year.
He said future levels are hard to predict because surges can be prompted by a range of factors such as stories in the news or banks rejecting a batch of complaints.
Around £13 billion has been put aside by financial institutions to compensate customers for mis-sold PPI policies, and the scale of the scandal has surged beyond expectations.
The FOS recently announced it was taking on an extra 1,000 case workers over the next year to help deal with the claims.
Around two-thirds of PPI complaints are upheld in consumers' favour and the FOS has previously criticised firms for dragging their heels over cases which could have been cleared up more quickly.
Earlier this month, the City watchdog confirmed it was in talks with banks about potentially imposing a cut-off point for people to complain about PPI, which was sold to people who did not want or need it and may have signed up to a policy without even realising.
The Financial Services Authority said it had been approached by the British Bankers' Association to discuss the potential for a time limit in return for the banking industry funding widespread advertising to raise awareness and ensure people know how to complain.