The council said if the thinner bin bags split then something would be done
Thinner bin bags have been brought in by a Kent council because of the rising cost of oil.
Sevenoaks council said its bill for the polymer-based bags would have gone up by £17,000 if it had not opted to cut the thickness of the sacks.
The density of the bags is being reduced by one micron - about 0.001mm.
The council said it had a set budget and it was not a cost-cutting move. But the Taxpayers' Alliance said councils could cut red tape instead of services.
Policy analyst Matthew Sinclair said: "Council tax has doubled over the last 10 years and families struggling to pay those mounting bills should be able to expect that basic services won't be compromised."
He said local authorities could cut back on bureacracy, reform expensive pensions, or scrap spending on "costly publicity spending".
I will use the bags myself and if there are any problems with them splitting, then something will have to be done
But councillor Avril Hunter said: "We, like many other local authorities, are already struggling to run our refuse freight.
"If we had gone £17,000 over our budget, then something else would have had to go to compensate for that."
She said that although the thickness of the bags would be reduced, they would have longer fibres to make them stronger.
And she added: "I will use the bags myself and if there are any problems with them splitting, then something will have to be done. I haven't had any complaints from residents so far."