Consumer group Which? has recommended that people do not buy third generation (3G) mobiles, which can be used for video calls.
Vodafone's 3G services can only be accessed by 60% of Britons
Its report says that UK network coverage for 3G is too limited to make the cost of the phones worthwhile.
Phone users should stick to existing handsets until 3G coverage improves outside big cities, Which? says.
But 3G firm Hutchison said it covered 80% of the UK population and accused Which? of "a lack of understanding".
Four years ago, mobile phone networks invested £22bn in the 3G licences.
Hutchison launched its "3" service in Britain last year, while Vodafone followed suit last month.
Two further competitors, Orange and T-Mobile, are expected to launch by the end of the year.
O2 has yet to confirm its 3G policy, although it recently announced that it would adopt the iMode service developed by Japan's NTT Docomo and now the backbone of that company's 3G offering.
Firms were hoping to claw back some of their investment in the technology in the run-up to Christmas.
Vodafone's 3G services can only be accessed by 60% of the British population at the moment, although it has pledged to increase this to 80% by 2007.
Meanwhile, Hutchison says its 3 network covers 80% of the population.
"There are teething problems with 3G phones and coverage so we recommend sticking with a 2G phone for the time being," Malcolm Coles of Which? said.
"We'll be keeping an eye over the coming months to see if they, and the
networks, live up to their hype."
Which? also describes some of the 3G handsets as "bulky".
But Edward Brewster, head of external relations at 3 Mobile, accused Which? of a
"lack of understanding" of the market.
He said: "On 3 Mobile, 80% of the British public can access our 3G video mobile services, that's 48 million - around 12 million more than our nearest competitor.
"And 99% can access our voice services and in ever increasing numbers."
Which? was also "mistaken" on the issue of quality and size of 3G handsets with the lightest weighing in at 114g and offering increased functionality, he added.
Vodafone has also questioned the findings of Which?.
"In terms of our coverage, we obviously haven't just thrown a network together," spokesman Ben Taylor said.
"Our coverage reflects the areas where we know people are most likely to use new types of service.
"At the first go, we're hitting a large amount of customers and we will continue to roll out the services."
It was "unfortunate" Which? had not had the chance to review Vodafone handsets because they had not been available when the study was made, he said.
"We believe our handsets address the criticisms made by Which?.
"The handsets are slick and small with long battery lives."