The report, conducted by Continental Research, suggests that 4oD's early launch date has given it the edge over its larger rivals.
4oD is used by 25% of internet TV viewers, while the BBC iPlayer is used by 16%. Sky leads ITV in the online stakes, with 12% of internet TV users watching Sky Anytime compared to 10% using ITV on Demand.
The past 12 months have witnessed the most activity to date in internet TV, with the BBC, Channel 4, ITV and Sky investing heavily in online content.
BBC and ITV internet TV projects are still at an early stage, while Sky Anytime differs by not making content available for free.
The BBC iPlayer got off to a rocky start this summer when a series of technical glitches led to criticism of the £131.2m project. 4oD launched in November 2006 and has turned to an ad-supported model to drive take-up.
The report also found that internet TV has far to go to become mainstream, despite rising steadily in 2007. According to the study, just 10% of UK internet users watched a TV programme broadcast via one of the online TV services in the past 12 months. People were less keen to download programmes and watch them later (8% of those surveyed did), while 15% of respondents had watched some form of internet TV.
The good news for online media owners is that 17% of the 1,000 people surveyed said they were very satisfied with their online TV services, compared with 12% who said they were unhappy with it.
The survey found that the main issues holding back greater take-up of internet TV were concerns about picture size and quality and sound quality.
Continental Research concluded that a further 2.4 million people are likely to watch TV on the internet in the next year. Of the respondents, 40% said that they were likely to use the BBC iPlayer.
James Myring, associate director at Continental Research, said that the BBC brand would ensure that people would experiment with the iPlayer. Whether they continue to use it or not was dependent on its usability, he said.
Internet TV specialists including Babelgum and Joost were not included in the survey.