If the two sold up, it would leave the ITV companies Granada and Carlton Communications, along with Reuters, in a three-way ownership split. All three are keen to increase their stake in the company.
The rule changes are currently being considered by Tessa Jowell, the minister for culture, media and sport, following the publication of the communications white paper earlier this year.
The news comes as ITN fights it out for the ITV news contract with the Channel 3 consortium, which comprises BSkyB, CBS, Bloomberg, Ulster TV and Chrysalis.