The figures were released by the Chartered Institute of Public Finance and Accountancy (Cipfa) following its annual survey of libraries in Great Britain.
Wales saw the biggest loss in the last year, with a fall from 308 to 274.
In England, the number of libraries fell from 3,142 to 3,076, while Scotland saw a drop from 573 to 567.
The closures coincide with government funding cuts of £50m to UK library services in the past year, from £0.99bn in 2013-14 to £0.94bn in 2014-15.
Rob Whiteman, chief executive of Cipfa, said the survey made "for grim reading".
"Cost-cutting measures continue to hit unprotected services hard and fewer people are using public libraries," he said.
Cipfa figures also showed library visits were down 3.9% from 276 million in the year 2013-14 to 265 million the following year.
However Cipfa was unable to say if the drop was a direct result of a loss in services or whether other factors, such as an increased popularity in e-books, were a cause.
A spokesperson for the Department for Culture, Media and Sport (DCMS) said that, despite the closures, there were still 225 million visits to libraries in England alone in the last year.
They added there had also been a number of new libraries opened in the annual survey period.
These included recently opened services in Stafford, West Midlands, and in Camberwell, south London. Meanwhile Arnold Library in Nottingham and Leyton Library in east London have been refurbished.
"We know that libraries continue to be popular but that people want different things from them. That's why the government set up the Libraries Task Force to help them improve things like digital access and e-lending," the spokesperson said.
"We have also made free wifi available in libraries around England and this year some new state-of-the-art facilities have opened, providing new technology to the local people they serve."
The Cipfa figures also showed spending on books, newspapers, periodicals and magazines in the last 12 months fell by 10.6% from £72m in 2013-14 to £64m in 2014-15, but that online and electronic expenditure increased by 1.7% from £11.6m in 2013-14 to £12.2m in 2014-15.
The number of libraries in the UK fell by 2.6% in the last year, from 4,023 to 3,917, according to a new survey.