Retailers have blamed rising shipping, freight and raw material costs for big increases in the prices of garden furniture over the past two years.
Consumer group Which? found some items were about twice as expensive as they were in 2019.
In one case it found the price of a shed sold by a leading DIY retailer was 155% dearer in 2021.
Retailers pointed to availability issues and said they were working with suppliers to keep prices down.
The “eye-watering” rises tended to occur at times when delays at UK ports were particularly severe, Which? said.
Customers were also facing items being out of stock and delivery days for multiple months.
Which? analysed 2,000 items across six major retailers – Homebase, Toolstation, B&Q, Amazon, Wickes and Screwfix – finding that on average prices had risen by 2% from July 2019 to June 2020 and by 9% from July 2020 to June 2021.
Sheds saw particularly large price increases, with one sold by Screwfix rising from £319.99 in July 2019 to £814.99 by July 2021, Which? said.
Wickes saw the largest average increase, with outdoor goods costing 13% more this year than they did in 2020. Screwfix and Toolstation also saw rises of over 10% across their garden products.
The other retailers checked were Homebase (8%), B&Q (7%) and Amazon (2%).
When asked by Which? what was behind the increase, B&Q and Homebase mentioned shipping costs, while a lack of raw materials – in particular timber – was also considered a factor.
Toolstation told the consumer group there had been a timber shortage due to “unprecedented demand in the US”.
Wickes pointed to “availability constraints and inflationary pressures”, while Amazon said some of its prices were set by third-party retailers.
Screwfix did not respond to Which?.
Ele Clark, Which? retail editor, said: “Many people have looked to spruce up their gardens with new outdoor furniture during the pandemic, but our analysis shows consumers have been hit with eye-watering price hikes for popular items.”
She said consumers should consider shopping around for the best prices and exploring the second-hand market as well as planning ahead due to large or custom items taking “several weeks longer than usual to arrive”.
New report finds big rises in garden furniture prices