Landlord mortgages accounted for 13.9% of new lending over the first three months of 2018.
Overall new loans increased by 3.3% year-on-year to £62.4bn, the data showed.
However, compared to the final quarter of 2017, lending fell 9.6%.
And new commitments – lending that has been agreed in advance in coming months – dropped 5.9% to £61.1bn.
Remortgaging edged up to account for 32.9% of lending with a value of £20.5bn, while new loans for purchases, including buy to let, dropped to 61.0%, driven by a fall in home movers.
First-time home movers
Within these figures, the share of first-time buyers has fallen to 19.6%.
The proportion of loan-to-income above four decreased as a share of lending in the quarter, as did the share of loan-to-value mortgages above 90%.
The proportion of total loans in arrears has also continued to fall with the outstanding balance in arrears now at £14.8bn.
Jeremy Leaf, north London estate agent and a former RICS residential chairman, said: “Although a little historic, the decrease in mortgage lending is disappointing. But of more concern is the fall in proposed advances.
“The reduction in the proportion lent to first-time buyers when buy-to-let investor borrowing increased for the first time in more than a year may be a sign that the government’s intention to ‘level the playing field’ between the two groups is not working.”
