Clydesdale’s complaints rocketed from 66 from January 1 to June 30 2010 to 410 in the latter half of the year.
Overall the bank received 2901 customers unhappy with its service.
The increase is related to the mortgage underpayment error the bank made last year that affected 18,000 borrowers.
Santander UK topped the list of mortgage complaints with 475 in six months, up from 434 previously, with 6759 complaints overall against the Spanish bank.
Behind Santander there was Bank of Scotland with 435 unhappy customers, out of 6743 for all areas of banking, compared to 500 in the first half of 2010.
Barclays Bank’s complaints dropped considerably from 473 to 368 out of 6535 complaints in total.
Meanwhile HSBC received just 86 mortgage-related complaints out of 6736 overall, reflecting a drop from 97.
Nationwide Building Society had 185 complaints, Cheltenham & Gloucester had 175 and Northern Rock Asset Management had 162