Saffron Building Society has put a hold on new mortgage applications due to a "record number" of applications.
From 5pm on Thursday August 4, the building society gave registered brokers 24 hours' notice to complete applications, saying the high number it had received was "putting pressure" on service levels.
Registered brokers have until 5pm today (Friday 5) to submit completed applications on behalf of their customers.
The only mortgage products not included in the temporary suspension are self-build mortgages.
According to Saffron, the "temporary pause" has been put in place to ensure existing applications can be "prioritised and brokers can get their clients into their homes as soon as possible".
But it comes less than a month since the building society lowered rates on its self-build products and reduced fees as part of its summer mortgage campaign for brokers.
The announcement also came on the day the Bank of England raised interest rates yet again, by 0.5 percentage points, prompting fears in the mortgage market.
Saffron's head of mortgage sales Tony Hall said the persistently "buoyant" property market had been affecting all lenders, with many seeing not just unprecedented, but record numbers of applications this summer.
Hall said: "All lenders are here to provide the best service possible for brokers and their clients. In recent weeks, as other lenders started to temporarily pause mortgages, we have seen an upward trend in applications that is putting pressure on our service levels.
"At Saffron, the service we deliver to our brokers is paramount and we are at the stage where this incredible level of interest is impacting applications that have already been submitted."
He added the decision to temporarily pause new applications would allow Saffron to concentrate on providing the "best possible service" to those applications that are already being processed.
Saffron Building Society launched Intermediar-ease, an initiative that provides openness and transparency around service because of its commitment to improve service for brokers and their clients.
While no end date for the suspension has been provided, Saffron said all existing applications would be processed as agreed.
It also encouraged brokers to keep checking its website for regular updates.
But brokers have already expressed concern over the combination of rising interest rates, which are now at 1.75 per cent, inflation which is predicted to hit 13 per cent, and the ongoing cost of living crisis in the UK.
Anderson Harris director Adrian Anderson said: "We have a mortgage interest rate ticking-time-bomb scenario.
"Circa 74 per cent of mortgages are fixed however it is likely these borrowers will be moving onto much higher rates at a time when many other outgoings have already increased.
"It is widely expected that over the short-term mortgage fixed rates will continue to be re-priced upwards, [so clients should] take action now and speak with an independent broker to discuss their circumstances and options.”