Almost 16,000 Dublin City Council customers have received warning letters after they failed to pay their refuse collection charges on time.

A further 1,500 cases are currently with debt collectors hired by the council to chase outstanding debts.

A spokesman for Dublin City Council said it typically allows customers 35 days to pay and issues a "gentle reminder" if payment is not made.

This letter was issued to 3,200 customers in June – a total of 15,800 have been sent since October 2008.

"If this does not prompt a response within 14 days we have the option of withdrawing the waste-collection service. If this happens, another letter issues a warning that the account may be passed to a debt collection agency in seven days," the spokesman said.

"If this goes unheeded the account is passed to debt collection… there are currently about 1,500 active accounts with the debt collector."

The spokesman said the council has operated a "generous" waiver scheme since the refuse charges were introduced in 2001. Some 40,000 households avail of this scheme at a cost of about €10m a year.

He added that the council has no cases currently before the courts in relation to refuse charges, and has not been to court in the past four years.

Meanwhile, Bord Gáis Energy has confirmed that it currently carries out around 350 to 400 customer disconnections a month, primarily due to failure to pay, while the ESB says it has disconnected around 3,000 business and household customers in the first six months of the year.

When asked how many of their customers have fallen behind in their utility bill payments, both energy providers refused to give this information, citing "commercial sensitivity" and confidentiality.

However, both confirmed that while they encourage customers experiencing financial hardship to contact them in order to work out a payment plan, they do expect outstanding debts to be paid.

They also confirmed that they use debt-collection agencies for customers whose accounts have been closed, but declined to say how many customer accounts have been referred to such agencies.

A spokeswoman for Bord Gáis Energy said it has noticed an increase in the time it takes its customers to pay their bills, with the average number of "debtor days" – or the length of time it takes a customer to pay once they have missed their original 30-day deadline – increasing by 10% this year when compared to 2008.

A spokesman for ESB said: "We encourage customers who are experiencing financial hardship to contact us early."