There was £88 million of new business conducted in May, according to the Finance & Leasing Association (FLA).
The total number of new agreements was 1,943.
New business in the 12 months to May 2018 totalled £1.025 billion.
Fiona Hoyle, head of consumer and mortgage finance at the FLA, said: “The May figures are consistent with the stable performance reported by the market in 2018 so far and are also in line with the performance of the wider mortgage market which reported new business steady in the first five months of 2018.”