Buy-to-let lending rose 3.9 per cent in May to £2.7bn, according to new data from Equifax Touchstone.
However, year-on-year figures were down 20 per cent, the data says.
Residential mortgage sales were more than £13bn in the month, up 4.4 per cent on April and 18.4 per cent year-on-year.
Combined, residential and buy-to-let sales for the intermediated market were £6.4bn in May, up 4.3 per cent from April.
Equifax data shows that the average residential mortgage in May was £194,404 (2015: £184,110), and £162,047 for buy-to-let (2015: £156,228).
Equifax Touchstone relationship manager Iain Hill says: “We are pleased to see the market has passed through the buy-to-let turmoil witnessed in the first quarter of the year and returned to steady growth. However, strong growth across both buy-to-let and residential sales has thrown June’s performance into sharp focus.
“Indicators are there that the current political environment and uncertainly could have a negative impact on sales.
“As the scale and longevity of this impact is still unclear, we will be closely watching the markets response to the outcome of the EU referendum.”
Equifax Touchstone data covers 92 per cent of the intermediated lending market