Up to a million homeowners could see their mortgage repayments jump by almost a third in the next 12 months as they approach the end of cut-price mortgage deals.

Four interest rate hikes in the past 10 months mean that borrowers are now facing a ticking time bomb as they near the end of two- and three-year fixed-rate mortgages taken out in 2005, which are now poised to shift on to more expensive rates.