Wave has withdrawn its nearprime plus range and increased its minimum age to 21 across all products.
In an email to brokers, the lender also says it will no longer offer buy-to-let mortgages to first-time buyers.
Director of distribution and sales Mehrdad Yousefi says that the tightening of criteria is a “housekeeping exercise”.
Yousefi says the firm has decided to withdraw its near-prime plus range to concentrate on prime niche, BTL and self-cert lending.
He says increasing the minimum age to 21 is a reflection that very few people under 21 want BTL or self-cert mortgages.
“This is just a housekeeping exercise. We are tidying up a few things that are currently out of sync,” says Yousefi.
A Wave spokesman says less than 2 per cent of its business applications come from under 21s.
Alexander Hall chief operating officer Andy Pratt says: “This could just be another way of trying to control the type of business they get in to improve the quality of their book.”