Shares in Carlton Communications were down 3.61%, a 3.75p fall to 99.75p, while Granada fell 2.6%, or 1.75p, to 66.5p, as fears mounted that a delay in the bill could hurt the merger of the two companies.
The bill is currently being debated in the upper chamber of parliament, the House of Lords. The Lords has threatened to block the bill if two clauses concerned with media ownership are not removed.
One clause would allow ownership of ITV by a non-EU company, which critics say could see the schedules filled with US programming and hurt the UK TV industry if a major US broadcaster took it over. The other would allow the proprietor of a large newspaper group, such as Rupert Murdoch, owner of The Times and The Sun, to acquire terrestrial station Five.
However, the ITV merger could still go ahead this year, even if the communications bill is held up. A spokesman for Carlton said the merger plans had been drawn up to ensure it would be able to go ahead even if the bill fails to become law by the end of the year.
The merger is currently being investigated by the Competition Commission, which is looking into whether it is anti-competitive. There is a great deal of concern that the merger will give ITV a dominant position in the airtime sales market, because it would control more than 50% of UK TV advertising.
One possible solution to the problem would be for the company to spin off one of its sales houses, although there are some who believe the companies could still collude to drive up the price of airtime, as they would be working for the same company.
The commission is due to report its findings on June 25.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the .