Portfolio Landlord exploitation?

I have come to the end of my 5 years fixed mortgage product. At the time of taking the Mortgage, there was no such definition of Portfolio or Non-Portfolio Landlord (the one who owns more than 4 properties). I simply decided to switch product with the same lender and I own exactly the same number of properties as I did 5 years ago.

When questioned by the lender, if I currently owned more than 4 properties, to which I answered “Yes”. The product which I fancied from their list was no longer available as they stated that, as a Portfolio Landlord, this product was not available, and they offered a product which was 1% higher than my choice.

My concern is that I did not ask for more borrowing there was no credit search as it was a simple product switch. How lenders can justify an extra 1% and why as a portfolio landlord I am penalised for something which was not applicable at the time of taking a mortgage with them?

As I already have a Mortgage with them, this is not as if there is an extra risk to the lender. In my view lenders are exploiting BTL borrowers because of Prudential Regulation new rules and as a result, my costs have gone up significantly not to mention S24 has already eaten up 20% of our profits.

Any views appreciated.

Simon