Complaints about mortgages or other secured loans rose to a record level in the last financial year.
Figures from the financial ombudsman service showed there were 13,659 complaints in the 2013/14 period, up 6% from the year before.
It urged lenders to take a less "black and white" approach to helping struggling borrowers, but also said many consumers were letting their situations get out of hand before seeking help.
The ombudsman said complaints centred on problems related to financial difficulties, meeting payment plans, or debt, and included the handling of arrears and repossession and recovery of shortfalls.
Consumers also raised issues about sales and advice on taking out mortgage products, problems with the administration of mortgages, upfront fees where no mortgage is offered, and disputes over valuation.
There were also claims about misrepresentation and misleading literature.
The ombudsman service, which exists to resolve disputes between consumers and financial businesses, said a third of those who made complaints had slipped into arrears before seeking help.
It added that it had told lenders they were expected to "get creative" in helping people get back on track with their finances, especially before payments are missed, but there was "still more they can - and should - do to help", it added.
The ombudsman said it upheld 30% of all mortgage complaints - but that on many occasions customers were seeking unrealistic outcomes such as suspending payments or interest indefinitely, or writing off debt.
Chief ombudsman Tony Boorman said: "Consumers and lenders all have a responsibility to work together when problems arise.
"And though it pays to be realistic about the options available to you, if your lender isn't listening, we're here to give you practical, honest advice to help sort out your problem."