MoneySavingExpert founder Martin Lewis has warned that homeowners are "at risk from a ticking mortgage time bomb".
Lewis said next spring could see a "triple threat" to people with mortgages, if the Bank of England puts up its base rate to 5% or 6%.
This base rate is now 2.25% - but was just 0.1% a year ago. This is factored in to the price of new mortgages.
Variable-rate mortgages go up in price almost straight away - though often lenders put up prices if they suspect a base rate rise is coming.
Fixed-rate home loans go up in price when they come up for renewal.
The Bank of England is predicted to put base rate up to help tackle rising inflation - currently 10.1%.
In a letter to the Telegraph, Lewis said: "If Britain's base rates continue to rise towards 5 or 6%, as the markets predict for next spring, we risk a triple threat.
"The impact on mortgage rates themselves; the fact that fewer people will pass affordability checks to get the cheapest deals; and that there could be a house price correction - with mortgage holders' loan-to-values dropping - hurting people's ability to secure the cheapest rates."
Lewis said he wanted to see "regulatory preparation and intervention to help protect people".
This could include changing remortgage rules so people find it easier to get cheap deals, he added.
Lewis's other ideas are to allow payment holidays and requiring mortgage lenders to make it easier for people to change their homeloan length.
"This needs investigating now, rather than waiting to see what happens, because, as recent evidence shows, prevention is better than cure," Lewis concluded.
But mortgage experts say that mortgage rates may be about to fall, after new Chancellor Jeremy Hunt took action to undo a lot of former Chancellor Kwasi Kwarteng's economic ideas.
Nick Mendes, mortgage technical manager at broker John Charcol said Mr Hunt's announcements "should signal a peak for the cost of fixed rate mortgages" but that "it makes it is less clear when they will start to fall.
Mendes said mortgage rates could also drop because lenders expect something called swap rates to fall.
The important point here is that the price of swap rates has been rising, and that means fixed rate mortgage costs are too.
When mortgage lenders give out home loans, they need to get that cash from somewhere.
In the old days, mortgages were mostly just the cash building societies raised in interest from customers' current account cash.
Now mortgage lenders get the cash they lend homeowners from several sources.
One of those is borrowing money from other financial firms, then paying it back with interest.
Swap rates are what mortgage lenders pay to financial firms to get the cash they then lend consumers to buy houses.
That affects fixed-term mortgages because lenders buy 'chunks' of money over two, three, five or ten years.
Anyone with a fixed rate mortgage will recognise those numbers straight away as the length of time a mortgage normally lasts.
Mendes said: "The fall in gilt yields, assuming it is maintained, will feed through to lower swap rates and hence reduces the cost of funds to lenders."
