Latest data from Moneyfacts shows that the typical time has dropped to 17 days - four days fewer than the previous-recorded low of 21 days in June.Eleanor Williams, a finance expert at Moneyfacts, said:
"This reflects the speed at which providers are updating their offerings, but also means that those looking for a new mortgage have the shortest length of time we have ever recorded to try to secure their deal of choice.
"It comes at a time when the Financial Conduct Authority (FCA) recently urged eligible borrowers to consider their mortgage options and switch to a more cost-effective deal to save money where possible.
"Prospective borrowers may need to move swiftly if they are to follow recent FCA guidance and are hoping to alleviate some of the pressure of the cost-of-living crisis by reducing their outgoings with a new mortgage deal."
The FCA said the number of mortgage borrowers not switching their mortgage deal when they could save money has declined significantly since 2016.
It now estimates that 370,000 people may save money by switching their mortgage but do not - down from 800,000 in 2016.
It has also calculated that around 110,000 would save less than £500 a year for two years, 110,000 would benefit by between £500-£1,000 a year and 150,000 would be more than £1,000 a year better off.
Ms Williams also said mortgage availability has dropped again this month.
August began with 4,407 mortgages on offer, which is 149 fewer than were available at the start of July.
The finance expert added:
"Would-be borrowers will also note that the rates on offer are continuing to climb. The average overall five-year fixed rate mortgage has breached 4% for the first time in nearly eight years - reaching 4.08% this month, a high not seen since October 2014.
"Meanwhile, the average two-year overall rate, currently 3.95% after another month-on-month increase, is the highest recorded in over nine years."
However, Ms Williams said the average standard variable rate (SVR) deal has also climbed - this month rising by 0.11% to 5.17%.
"While the differential between this and the average fixed rates now available has shrunk, it's clear that those on, or about to revert to an SVR, could save on their monthly mortgage repayments if they are able to lock into a new fixed deal.
"The amount a borrower might be able to save on a new mortgage will depend on many factors, and it's important consumers remember that average rates reflect what's available across the whole of the market - and therefore there are still products offering even- more-competitive rates and packages on offer.
"The support and advice of a broker in finding the best option for an individual's circumstance and in helping to assess their eligibility has likely never been more vital as the mortgage landscape remains extremely changeable."
