Only just over half of providers have actually upped their SVR since the base rate was last month hiked to 0.5%, according to analysis by Moneyfacts.co.uk.
Most of the major lenders have increased their default rates but overall the average SVR hike has only been 0.14%, compared to the Bank of England increase of 0.25%.
This appears to be an attempt to not shock borrowers into remortgaging, Moneyfacts suggests.
However, tracker rates have seen a far starker average increase, with the average two-year deal rising from 1.77% to 2.02% over the month.
Charlotte Nelson of Moneyfacts, said: “Historically, a base rate rise would mean that all variable rates would increase too – and it would be more of a question of when, not if, they would do so.
“However, this time, providers who are keen to be seen on the side of the borrower may have opted to either not increase by the full amount, or not pass on the rate rise at all.
“Providers know that a base rate rise will spark an interest from borrowers to remortgage for a better deal, so they will want to minimise the number of borrowers switching to other lenders by keeping their SVR the same.”
The typical SVR rate is now at 4.74% from 4.6% in November.
Nelson added: “Borrowers may feel they are getting a reprieve from the full effects of the base rate rise, but when the highest SVR is currently priced at 6.08%, it may be little consolation to know that some SVRs have not seen a rate rise.
“The smaller than expected rise to SVRs shows that perhaps the base rate had more of an impact on the mindset of the Bank of England and providers alike than on the rates themselves, which may set the ball rolling for further rate rises in the future.”