Over three million borrowers in the UK do not know what rate of interest they are currently paying on their mortgage, a new survey has found.

Around a third of borrowers are repaying their mortgage at their lender's Standard Variable Rate (SVR), according to research from the Post Office.

Yet 29 per cent of those people are only assuming their SVR rate is the best one for them, the Post Office claims.

Staying on a SVR may seem the easiest thing to do, but may be able to save money elsewhere, says the Post Office's personal lending director Marco Hughes.

"If you're thinking about switching mortgage, now is the best time to do it, before rates rise further. With many SVRs at or above four per cent there are already better deals to be had out there," he added.

Today, Santander announces reduced rates on it's 80 per cent loan-to-value mortgages, with two-year trackers available at a rate of 3.25 per cent.

Santander lent one in five UK mortgages in 2009.