The possibility of the interest rate starting to rise is causing worry for a number of mortgage borrowers, it has been said.

Michelle Slade, spokesperson for Moneyfacts, revealed that the demand for fixed-rate products has increased as a result.

"While fixed-rate mortgages are cheaper than they were last year, they are not as cheap as we would have normally expected as the lenders are taking a larger margin for risk," she warned.

Lenders are increasingly more likely to see customers defaulting on their mortgages, which is made worse by the rising rate of unemployment.

Tracker customers will be hardest hit by fluctuations in the base rate, Ms Slade emphasised, with some borrowers likely to struggle with interest rates once they escalate to around seven per cent.

Moneyfacts reported on June 22nd 2009 that the average two-year fixed-rate mortgage deal increased by 0.16 per cent in the previous week to 4.90 per cent.

The average five-year fixed deal has increased even further, it added, rising from 5.61 per cent to 5.82 per cent – a five-day jump of 0.21 per cent.