East Midlands Housing Association, which is the landlord for thousands of people in Northampton, has made the changes for people who have shared ownership of their home. The rental part of the monthly charge is to rise by 3.2 per cent.
Service charges are also set to rise at the same time.
One resident who lives in a Northampton town flat owned by EMH said the large increases went against the ethos of a housing association.
He said: "My own rent will go up more than £40 a month. Service charges are going up nearly £30 - and we get nothing extra.
"It's supposed to be not for profit. i don't see how they can justify those increases.
"It's adding insult to injury.I don't feel comfortable having them as a landlord now."
A spokesman for EMH said: "I can confirm that shared ownership rents have increased by 3.2% under the terms of the shared ownership lease and the Retail Price Index.
"We wrote to all shared owners in early January explaining the increase and that the change would be effective from 1 April."