From today, the mutual will compare its rates for existing customers against the best remortgage deals offered by high street rivals NatWest, RBS, Halifax, Santander, HSBC, Barclays and Lloyds each week.

If any of those products are found to undercut the rates offered by Nationwide, the lender will reduce its rates accordingly the following Wednesday.

Existing Nationwide customers are already able to access a 0.1% discount on new rates.

To be included in the loyalty rate scheme mortgages must have the same product term and comparable fees. Intermediary exclusives, buy-to-let, Help to Buy and those products with fees of more than £1,000 will be excluded from the scheme.

Nationwide divisional director of mortgages and savings Richard Napier said: “Following our recent extensive reductions across our mortgage range, Nationwide’s mortgage deals for existing customers are already extremely competitive.

“With loyalty rate mortgages, we are taking that a step further. We are constantly reviewing the market so that our existing mortgage customers can be confident our rates compare favourably against those of our competitors. We are doing the work for them by checking the rates of the top six lenders to make sure that we offer the best rates.”