Ultra-low mortgage rates have already been vanishing amid expectations that the Bank of England base rate could increase soon.

On Thursday, the Bank will reveal whether it will hike the base rate amid pressure from inflation or maintain the existing 0.1% rate for at least one more month.

On October 25 there were 82 fixed-rate mortgages available at 0.84% to 0.99% but by Tuesday this week this had shrunk to 22 deals, according to analysis by Defaqto.

Last week the average two-year fixed mortgage rate for a first-time buyer putting down a 5% deposit was 2.45%. This has jumped over the past week to 2.69%, the financial information website added.

Around a quarter (26%) of homeowner mortgages are variable rates, according to trade association UK Finance. These deals would be the most exposed to the immediate impacts of any increase in the base rate.

This group includes 850,000 tracker mortgages, with rates that generally follow the Bank of England base rate, and 1.1 million standard variable rates (SVRs).

SVRs are set individually by lenders, and they are the default products that borrowers end up on once their initial mortgage deal has ended.

Around three quarters (74%) of mortgage borrowers are on fixed-rate deals and so would be protected from the immediate impact of any base rate increases.

This group includes the overwhelming majority of more recent borrowers – 96% of homeowner mortgages advanced since 2019 were fixed rates.

UK Finance said that as most new mortgages are fixed rate, the stock of variable rate mortgages tend to have lower balances on average as so many were taken out a significant time ago.

Homeowners on tracker mortgages have an outstanding balance of £124,000 on average.

Those on an SVR owe £77,000 on their mortgage typically.

People on a fixed deal have an average balance of £159,000 outstanding.

A quarter point rise in the base rate, for example, could mean an extra £26 per month mortgage payment on average for a tracker rate customer and £16 for those on an SVR, according to UK Finance’s calculations.

Katie Brain, consumer banking expert at Defaqto, said: “We have enjoyed record low interest rates for a long time and they had to start going back up at some point. For anyone who needs a mortgage, there is never a good time for this. However, interest rates are still very low compared to previous years and there are still some great deals to be had.”

She added: “Sometimes any saving on the headline interest rate can be wiped out by expensive fees and you need to know what the cost is over the whole period you are tied in for.

“It is always worth getting independent advice from a professional who can advise you on the right product for your needs.”

A base rate increase could mean improved rates for savers, although experts cautioned they may not see any immediate difference.

Sarah Coles, senior personal finance analyst at Hargreaves Lansdown, said: “We need to track down what we’re making on our savings, and if we’re earning next to nothing we should keep our eyes peeled for better deals from smaller and more competitive banks in the immediate aftermath of a rate rise.”

Sarah Pennells, consumer finance specialist at Royal London, said: “There’s no guarantee that the interest rate on variable rate savings accounts will rise straight away, so savers should keep a close eye on their own rate. In the event of a rate rise, other banks or building societies may offer a better return.”

Helen Morrissey, senior pension and retirement analyst at Hargreaves Lansdown, said an interest rate rise could also have a positive impact for people buying annuity retirement incomes.

She said: “After years in the doldrums, annuity rates have been on the rise throughout 2021, and recently hit a two-year high. If the Bank of England chooses to raise interest rates this could give annuities a much-needed further boost towards the end of the year.”

Ms Morrissey said that when interest rates rise, investors often sell government bonds as they can achieve higher returns elsewhere – and bond prices fall. Annuity rates tend to rise – as providers use government bonds to provide annuity incomes.