Fixed rate mortgages have fallen continuously for the past six years - with marked falls taking place before the Brexit vote.
Rates have fallen by an average of 2.5 per cent since 2010, according to data released today from Legal & General.
For two-year fixed mortgages, annual monthly fixed rates have fallen by 2.23 per cent, while rates on five-year fixed morgages have decreased by nearly three per cent.
Legal & General said there was a "marked" fall in fixed rates in the period leading up to the Brexit vote due to "speculation that the Bank of England would opt to reduce the base interest rate following the result".
Jeremy Duncombe, director of Legal & General mortgage club, said: "It's clear from these results that the Bank of England's base rate is not the defining factor in deciding mortgage interest rates. There has been a consistent and a substantial fluctuation in fixed rates since the 2009 decision to bring the base rate to an historic low level.
"Instead, it's external factors, including the availability of capital and the strength of the economy that play a significant role in fixed rates."
HSBC launched a record low fixed-rate mortgage in June, offering a rate of just 0.99 per cent for two years - but experts slammed the product as a marketing move that shut out most borrowers.