DESERTING your lender for a new suitor is the norm when remortgaging, but what many borrowers do not realise is that their current lender may have a secret range of unadvertised deals that are competitive enough to make them stay.

Mortgage advisers say that these “behind-the-counter” deals may not be the keenest on the market, but they are much less punishing than the standard variable rate (SVR).

Experts suggest that about half of all borrowers are needlessly paying their lender’s SVR, which is the expensive rate to which mortgages typically revert once initial offers have expired. Borrowers often stay put because they cannot face the hassle involved in remortgaging and they do not want to shell out fees for legal work and valuations.

Deals that are designed to encourage existing customers to remain loyal are known as “business retention mortgages” and who will be offered one of these, sometimes secret, deals varies from lender to lender.

David Hollingworth, of London & Country Mortgages, the broker, says: “A few years ago lenders were very cloak and dagger about what they would offer existing borrowers. Today many lenders have become more open, but there are still those that are rather cagey about their business retention deals.”

One large lender that is very reticent when quizzed about its offers is Abbey. Apart from customers who opt for its Flexible Plus offset tracker mortgage, the lender cherry-picks the customers it wants to retain. Only a select band of desirable borrowers can expect a call from business retention agents hoping to make offers that they cannot refuse.

What is more, Abbey will not disclose the rates it offers, and these rates vary from customer to customer.

This is not a problem if you fit the profile and are enticed to stay with a solid rate. However, it is not so good if you, or a broker working on your behalf, is trying to search the mortgage market, including your current lender’s offerings, for the best remortgage deal possible.

Rob Clifford, chief executive of Mortgageforce, another broker, says: “We don’t know what deals are on offer until we ask, and rates can depend on the amount of equity in a customer’s home, the type of mortgage preferred and the client’s payment history.”

Growing numbers of lenders, including Nationwide, Woolwich and NatWest, offer the same deals to new and existing customers, while other lenders, such as Portman Building Society, have specific business retention deals but make them available to all customers and are upfront about rates.

Matthew Wyles, group development director at the Portman, says: “We write to all customers with maturing mortgages with deals carefully priced to negate the cost of remortgaging elsewhere.”

For example, existing Portman customers have access to a two-year fixed-rate deal at 4.69 per cent with a £499 arrangement fee or a five-year fix at 4.99 per cent with a fee of £199.

Halifax is also clear about the rates available to existing customers. Prices compare well and some packages are even better. For example, existing customers can secure a two-year fixed-rate deal at 4.99 per cent with a £299 fee, while new customers must pay £499 for the same rate.

If your lender is less upfront, but you are keen to avoid the inconvenience and cost of switching lenders, be prepared to haggle.

Chris Cummings, of the Association of Mortgage Intermediaries, says: “It is always worth refusing the first offer and it might pay to walk away again. Advisers can do this for you as well as use their knowledge of what other existing customers are being offered to get the best rate.”

Customers who want to avoid ever having to pay the SVR should take the initiative and start negotiating before their deal comes to an end.

If you can secure a satisfactory rate from your existing lender, the other key advantage is that you will probably be able to organise your new mortgage with one phone call and by posting back only one piece of paperwork.

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