The Office for National Statistics said that this was down from 8.6% rent increase in the 12 months to July this year.
Breaking down the rises between the nations, average rents rose by 8.5% in England, and now stand at £1,327 per month.
The same rent increase of 8.5% was seen in Wales, but as rents tend to be lower in that region, it brings the average value to a significantly lower £752 per month.
A smaller rent increase of 7.6% was seen in Scotland during the 12 months to August this year. It brings rents in that region to just shy of the £1,000 a month mark at £969.
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Rental rises continuing but pace slowing
Aimee North, ONS head of housing market indices, said: “Rental prices continue to climb at a near-record rate, although the pace of the increase has slowed slightly.
“London again saw the fastest growth in rents, with the slowest rise in the South West of England.”
In England, the growth in rents was highest in London at a massive 9.6% and lowest in the South West at 6.4% during the 12 months to August this year.
Nathan Emerson, chief executive at Propertymark, said: “The rental market continues to operate with a very strong headwind, as many landlords battle increased overheads and uncertainty regarding future legislation.
“Landlords have faced a complex combination of high inflation, interest rates, maintenance costs and a more demanding taxation structure over the last few years.
“In turn, this has had a profound impact on their ability to operate and in some circumstances has forced good landlords to make the difficult choice to sell up and leave the sector.
“To keep rental costs across the UK sustainable, Propertymark is keen to see a progressive approach to future housing strategy and a plan that encourages long-term investment.
“With an ever-growing population, it is imperative that supply keeps up with real-world demand and that future planning carefully considers key regions where demand is most prevalent.”