Apple's iPad is under threat from smaller and cheaper Android tablets like the Google Nexus 7 and Kindle Fire.
Android tablets are seen by the public as 'premium' devices on a par with Apple's iPad.
A recent YouGov poll revealed that 63% of tablet owners in the UK have an Apple iPad, making it by far the most popular device of its kind.
However, in a similar study conducted a year earlier, iPad ownership was 73%.
This apparent slump in Apple's market share is thought to have been caused by the rise of Android tablets - including the Google Nexus, Samsung Galaxy and Kindle Fire product ranges - that offer a high-quality alternative to the iPad.
John Gilbert, consulting director of YouGov Technology and Telecoms, said: "Consumers rate the Samsung Galaxy tablets equal to iPads in terms of quality.
"It seems that Apple no longer has a monopoly on the 'premium' share as other brands emerge with near-equal satisfaction scores.
"Given the market's current expectations and considerations in purchasing tablets, we anticipate Apple will lose additional share throughout the coming year to Samsung, Google and Amazon."
Findings published last month by the International Data Corporation (IDC) show the Apple iPad's market share could soon fall behind that of Android tablets.
Shipments of Apple's tablet are forecast to dip below 50% of the market this year, as smaller and cheaper devices prove an increasingly popular choice.