A total of 1,181 households are behind on their rent, compared with 1,070 last month, according to Independent Cllr. Maeve Yore.
At a monthly meeting, Cllr Yore highlighted that in one month alone, the amount of rent arrears had risen by over €348,000.
840 tenants owe more than 12 weeks of rent and 945 are paying by household budget.
Chief Executive Joan Martin assured the councillors that rent arrears are something they keep a close eye on and a strong system is in place for following up on such cases and putting payment plans in place.
She added that a detailed report would be prepared for their next meeting in September.
Head of Finance Bernie Woods added that repayments are made through An Post and as there is always a time delay in payment received through An Post, it was possible the way the month fell, accounted for the increase.