Martin Lewis is urging mortgage customers to check if they can lock into a cheap deal now over fears rates could rise.
The MoneySavingExpert founder pointed out how mortgage rates are at an all-time low with the cheapest fixed deal right now being 0.84%.
But personal finance and market experts have sounded an alarm over interest rates with predictions that they will rise from 0.1% to 0.25% this week.
This means anyone on a tracker and variable rate mortgage - where your rates go up and down - would see their mortgage bills rise in line with interest rates.
Martin also predicts how cheap fixed rate deals could rise as well if inflation continues to stay high, combined with quantitative easing coming to an end in January.
Have you managed to save £1,000s by locking into a cheap mortgage deal? Let us know in the comments below
"What will happen to the cheap deals you get is a little more complicated," he explained on Radio 5 Live today.
"Normally the rate of the cheapest deals tend to follow what are called the city swap rates, but over the last year or so, the mortgage rates have been relatively low compared to the swap rates.
"That’s likely due to two things. First, increased competitions, and second, the banks have a glut of cash due to quantitative easing, which is the government printing money, if you like.
"But quantitative easing is due to end in January, so if interest rates go up, expect to see a quick start in the mortgage rates increasing.
"If inflation continues to stay high, I think we will continue to see them creep up which means we’ll see mortgage rates go up."
The Bank of England monetary policy committee, which votes regularly on what the base rate should be, will next meet this Thursday (November 4).
If there is a rate rise, it will be announced that date.
Writing in one of his latest MoneySavingExpert newsletters, Martin urged everyone with a mortgage to check now and see if their existing deal is as good as it can get.
MoneySavingExpert issued the following tips on how to check if you’re on the best deal:
Find out your current mortgage deal
You’ll need information such as your current rate, the length of deal and what type of mortgage you’re on.
It is also important to check whether you’ll be penalised for switching deals now.
If you're unsure of the details of your current deal, call up your lender and ask them to provide the information.
Ask for your existing lender's cheapest deal
Once you know more about your existing deal, ask your lender what the cheapest deal it can offer you is.
MoneySavingExpert explains this is called a "product transfer" as you're not changing provider.
Just make sure you won’t be borrowing more in the long run, otherwise it may not be worth changing.
Compare this to the best market deals
Finally, use a free mortgage calculator to compare your lender's best rate against other deals on the market.
Do note that low-rate deals can mean higher fees, so take this into account as well.
If you do decide to switch, you may now be wondering whether now is the right time to fix into a deal.
Of course, it depends on your individual circumstances and the type of deal you're offered by your lender.
But MSE notes: "The more you value certainty and being able to stick to a budget, the more you should hedge for a fix, and fix longer.
"If you're worried about interest rates rising... then fixing is a bit like an insurance policy against this.
"Trackers may be a smidgeon cheaper, and if today's rate is your prime concern and you can ride out moves, you may want to go for it."
