The cut reflects the failure of thousands of people to pay the Household Charge.
Councillors were told in a letter also showed that there has been a large increase in the number of people paying the €100 tax – with 47% of people now having settled the bill.
That leaves just over half the householders in the county – 53% – who haven’t paid.
The Department of Environment letter to the council and its councillors says that if more people pay up, more funding will be released.
However it warns councillors that they should re-forecast is spending plans for the rest of 2012 “to ensure a balanced budget.”
Dozens of protestors are today lobbying councillors over the tax.