For many households the benefits of yesterday's mortgage cuts could be modest. The 4.2 million homeowners on existing mortgage deals pegged to the base rate - about a third of the UK mortgage market - will be celebrating this weekend. Their mortgage repayments are guaranteed to drop on December 1.

But the outlook for those wanting mortgages that track the base rate is less certain. Lenders were quick to withdraw their tracker deals for new customers after the Bank of England's surprise announcement. New deals will appear next week but the margins are likely to increase. Fees may also rise to offset the rate cuts that banks reluctantly agreed to yesterday. Borrowers should also check the small print on their existing tracker deals. Some lenders have written clauses into them preventing the rate falling below 3 per cent.

Experts believe that there could soon be a move away from loans tagged to a low base rate. Industry experts have started discussing mortgages linked directly to Libor, the money market rate that banks use to fund new mortgages, which is more than one percentage point higher than base rate. The practice is already common in the sub-prime market.

Lenders could also become more aggressive at pushing their discounted deals linked to the standard variable rate (SVR), which they can control. Yesterday Derbyshire Building Society launched a new discounted deal pegged to the mutual's SVR and further discounted deals are expected in the coming weeks.

Experts also say that lenders could introduce additional clauses to new deals that could give them greater room for manoeuvre in the face of a falling base rate.