NatWest is increasing interest rates on its entire core and broker exclusive buy-to-let (BTL) product ranges.
Every loan in the two ranges is increasing by 70 basis points, with the changes affecting almost 50 deals.
The changes come into effect 16 October.
Meanwhile, Barclays is increasing interest rates on five new business residential mortgages and withdrawing two large loan deals.
It is also significantly raising rates on more than 50 residential and buy-to-let mortgages for existing customers, with some deals increasing by up to 45 basis points.
Brokers will need to reserve one of the amended or withdrawn products today and will then have nine days to secure a case booking and submit a new lending application.
The five new business products being increased include one at 85 per cent loan to value (LTV) and two at 80 per cent LTV.
The five-year fix for purchase with no fee at 85 per cent LTV is increasing by 10 basis points to 3.3 per cent.
Meanwhile, the purchase and remortgage deals with a £999 fee at 80 per cent LTV are increasing by 26 basis points to 2.25 per cent for a two-year fix and by 21 basis point to 2.45 per cent for a five-year fix.
The two-year and five-year fixes at 75 per cent LTV for loans above £500,000 are being withdrawn.
A Barclays spokeswoman said: “We regularly review our products and earlier today we announced to mortgage brokers that some products will change.”