The Financial Ombudsman Service said it had logged 211,885 PPI claims in the six months to December 31, up from 86,000 in the previous six months, with the total number reaching 600,000.
A financial watchdog is receiving 2,000 new payment protection insurance (PPI) complaints a day as overall grievance figures hit record levels in the second half of last year.
The surge in work in the wake of the scandal, which saw many people finding they had taken out insurance to help pay back their loans after a loss of income without realising it or under pressure, forced the watchdog to take on an extra 1,000 case workers from January.
Taxpayer-backed Lloyds TSB topped the table of PPI complaints, with the ombudsman upholding 86% of the 42,195 complaints against the lender.
Natalie Ceeney, chief executive and chief ombudsman, said the number of PPI complaints had continued to increase at "unprecedented levels".
She said: "Over the last year or so, we have geared up substantially to deal with these record complaint numbers and we are now resolving more cases each week than ever before. However, as the complaint levels show no sign of slowing, consumers are increasingly having to wait longer to get their complaints sorted - with many businesses still continuing to cause unnecessary delays."
The watchdog said five financial services groups accounted for 78% of all new PPI cases received between July 1 and December 31 2012. The top five most complained about were: Lloyds, Barclays, Bank of Scotland, MBNA Europe Bank and Capital One.
Overall complaints figures reached a record 283,251 in the second half of last year - a 110% increase on the previous six months. Lloyds Banking Group was the most complained about business group with a 237% increase in overall complaints to 93,454.
Barclays was complained about 45,532 times and Royal Bank of Scotland, which is also taxpayer-backed, had 19,214 complaints made against it.
Which? executive director Richard Lloyd said: "It's shocking that the number of PPI complaints to the financial ombudsman has more than doubled in six months, now reaching record levels. Some banks are clearly not making it as straightforward as they should for people to get the money back they're legitimately owed. Banks must deal with complaints quickly and fairly and help consumers claim the compensation they are due without hassle. They should be proactively contacting past PPI customers so people are aware they can claim without using unnecessary and expensive claims management companies. And the Financial Services Authority should take action against any bank dragging its feet in settling complaints."