A three-year low in inflation last month is likely to ease a little of the borrowing strain in this month's Budget for the government, as it means state benefits will be increased by a smaller amount.
September's rate of consumer price inflation is used to work out how much benefits will increase the following spring.
Families of working-age on universal credit will therefore get a 1.7% or £253 hike to benefits next year, according to calculations by the Resolution Foundation.
Lalitha Try, economist at the thinktank, said: "There was a larger-than-expected fall in inflation last month, but it will rise sharply in October driven by base effects from energy prices.
"This temporary fall is badly timed for millions of low-to-middle income families as will result in a lower increase in their benefits next year."
Try said the government "needs to address the age divide in benefits which has left working-age support fall further behind rising wages and living standards".
She noted that as October inflation is expected to pick back up as falls in energy prices last year drop out of the 12-month calculation, means the same family would see their UC award rise by £327 instead, a cash gain of £74.