At this week's planning committee, the developers tried to renege on that agreement. They said renovating the flats would cost too much and, instead of their original commitment, offered the council £20,000 as a one-off payment.
This did not go down well with councillors.
Plaid Cymru councillor Marc Jones, who sits on the planning committee, said:
"The money being offered is an insult and will mean there are four fewer affordable homes for people locally. It's regrettable that officers seem willing to bend over backwards for developers, who are talking in millions but seem unable to contribute a tiny part of that for much-needed affordable housing."
The decision was deferred for a month for further investigation but Plaid councillors are insisting that the original agreement is maintained, with four affordable homes or their equivalent being provided by the developer.
Cllr Jones added:
"Few people will have sympathy with the developer pleading poverty on this matter. A deal is a deal and a providing four flats is hardly going to break the bank."