The lenders said that current processing delays were due to its products proving popular direct borrowers and mortgage advisers.

Gary Brook, head of corporate communication at Leeds Building Society, said that the lender was taking action to increase capacity and remove the backlog of applications.

“We have already invested to increase capacity, are working overtime to meet demand and are reviewing our processes to maximise efficiencies.”

Recent financial results released by the society showed it had increased lending by more than a third during 2012. Leeds has also made significant use of the Bank of England’s Funding for Lending Scheme.

Brook added that the society was trying to make customers aware of the delay.

“Our current mortgage range is proving very popular and, as a consequence, we are slightly out of service standard on post and first assessment, which are two and three days over respectively,” he said.

“Our service standard position is updated daily on our website so intermediaries are aware of the current position prior to submitting an application and throughout the process.”