Almost half of consumers who have bought goods online over the last two years have experienced a problem with their purchase.
That's according to new research from Which?, which found that for 46% of online shoppers the buying process had not gone smoothly.
The three most common problems with shopping online were deliveries arriving late (19%), goods being faulty or damaged on arrival (13%) and goods not arriving (12%).
One in 10 (11%) had their delivery left outside their home without permission and 4% said they were charged an additional or unexpected fee when shopping online.
The most frequently-mentioned online retailers that shoppers experienced problems with were Amazon (34%) and Ebay (29%).
Which? has a free consumer rights website to help shoppers know what they are entitled to when shopping on websites.
Said Which? executive director Richard Lloyd : "With people increasingly shopping online and millions experiencing problems with their purchases, it is vital that consumers know their rights on late deliveries and faulty products."
Almost half of consumers are now buying more clothes and footwear online than they did two years ago, while 37% buy more DVDs, games and CDs online and 33% buy more electrical goods.