Lloyds was the most complained-about mortgage and home finance brand in the first half of the year, with 769 new cases received, according to the Financial Ombudsman Service.
The second was Santander UK with 563, then Barclays with 473, Nationwide with 433 and NRAM with 325.
NatWest was the sixth most-complained about firm, with 280 objections logged.
Following NatWest were RBS with 161 complaints, HSBC with 157, Cheltenham and Gloucester with 119 and Mortgage Express with 101.
However, the lender with the highest proportion of mortgage and home finance cases upheld against it during the first half was Legal & General Partnership Services.
The FOS found for the consumer in 92 per cent of cases against the lender.
Following L&G was Countrywide Principal Services with 58 per cent of cases upheld, then Connells with 57 per cent, Leeds Building Society with 42 per cent and the Co-operative Bank with 41 per cent.
Following the Co-operative with Barclays, with 38 per cent of cases upheld in the period.
Then came GE Money Home Lending and Santander UK, both with 37 per cent, then Cheltenham & Gloucester and NatWest, both with 35 per cent.