A committee of MPs has said plans to expand Channel 4's remit could increase its market impact "significantly" and urged the Government to examine what controls should be in place.
The House of Commons Culture, Media and Sport Committee also suggested that if the broadcaster ends up performing similar functions to the BBC then both could be governed in a similar way.
Proposals were made to expand Channel 4's public service broadcasting (PSB) remit to also include digital channels E4, More4, Film4 and other online services.
The committee said the Government's Digital Economy Bill could make Channel 4 more like the BBC, with both providing public service content on a network of services, although unlike the BBC, Channel 4 generates all of its revenue commercially.
In the Channel 4 Annual Report, the MPs said: "The extension of Channel 4's primary functions beyond the core PSB television channel, along with the growth of its non-PSB activities, means the market impact this public organisation has might increase significantly, raising questions about how this market impact should be monitored and controlled.
"We recommend that the Government consider and address these issues now, during the passage of the Digital Economy Bill."
The report also said it was "far from clear" that PSB content levels had been properly examined and at times Channel 4's output appeared to be "composed largely of non-PSB programming".
It listed Channel 4's shows on December 1 2009, which included US comedies like Frasier, Friends, Will and Grace, The Simpsons and Ugly Betty as well as British film classic Carry On Doctor and UK content such as Deal or No Deal, Countdown, Channel 4 News, Hollyoaks, The Queen and The Paul O'Grady Show.
In 2008 Channel 4 spent £153 million on first-run UK-originated programming on key PSB shows. The report continued: "However, this comprised a minority of the £390 million expenditure on UK-originated programming, and an even smaller proportion of the total expenditure of £516 million on programme and other content on the channel."
The report said the figures and sample schedule "would appear to support criticism from the media commentator David Elstein that Channel 4 is 'a small public service dog being wagged by a very large commercial tail'".