New research has revealed that lenders are restricting one quarter of deals on home loans to their existing customers.

Research by market analyst Defaqto showed that the number of mortgages has increased significantly from 1,686 up to 2,948 from last July.

However, the research also showed that 26% of the home loans offered could only be taken out by existing customers of the bank or building society that was offering them.

10% of the mortgages offered are restricted to people who have their home loan with that particular lender while a further 15% are only available to customers who hold a current account with that particular bank or building society.

An insight analyst from Defaqto said: "While it is no surprise to see that almost 10% of mortgages are restricted to lenders' existing mortgage borrowers, there has been a noticeable move by the major lenders to launch mortgage deals that are only available to their current account holders.

"The banks are clearly keen to further their ambitions of becoming one-stop shops for all their customers' personal financial product needs and offering special mortgage deals to their current account customers is a definite part of this strategy."

The research also found that customers were being tempted by lower mortgage rates in deals that were exclusive rather than those available to all customers.