A council in East Yorkshire has set aside £35,000 to settle its debt after finding out it had failed to pay a gas bill for 17 years.
The authority is still waiting to find out what its final bill will and utility company Northern Gas Networks has yet to confirm whether Ofgem rules limiting back billing to no more than 12 months apply to the council.
Councillors believe the final amount will be lower than the amount they have allocated to cover it.
But Liberal Democrat Denis Healy, chair of the Town Council's personnel committee, said it was "completely unacceptable" that the problem had gone unnoticed for so long.
Mr Healy said: "The £35,000 is unspent money the council's been able to carry over, there's no way I'm expecting the final bill to be anywhere near that.
"It was an underspend from previously and after we've settled this we'll spend what's left of it on local services and projects in the town.
"We're not going to be doing a whip round asking the people of Beverley to pay our gas bill.
"The key question is how far back we're going to be billed, there's limits for domestic customers but we don't know if they apply to businesses or councils."
He added: "The public rightly want answers about this and as elected councillors we have a responsibility to look into this and ultimately do the right thing."