Tessa Jowell and Patricia Hewitt have been accused of "dogmatism and hate" in their response to calls for the new media regulator to have greater powers.

Lord McNally, the Liberal Democrat's spokesman in the Lords, slammed the attitude of the culture and trade secretaries towards the Puttnam report into the new media regulator Ofcom.

The peer, who was a member of the committee that wrote the report, told ePolitix.com he was "appalled" at the attitude of the two cabinet ministers to proposals for the new regulator to investigate major takeovers of media firms.

"Quite frankly I am appalled that when Puttnam came out with his quite modest recommendation of Ofcom being allowed to look at big mergers, within an hour Tessa Jowell and Patricia Hewitt were on the air rubbishing it," he said.

"I wonder why there is such dogmatism and hate about the future about both Channel 5 and ITV when these are important decisions which Ofcom should be competent to look at in the public interest."

He predicted that the government could face a rebellion in the Lords unless it was prepared to think again about increasing the media watchdog's powers.

"I think that there will be an amendment carried in the House of Lords and then the government will have to make up its mind on whether it wants its bill with the amendment or whether they want to fight us on this," the peer said.

Lord McNally's comments came as the two secretaries of state announced the appointment of Urmila Banerjee, David Edmonds, Richard Hooper and Sara Nathan as non-executive members of the board of Ofcom.

The Lib Dem peer also warned ministers that the future of ITV was serious and urged caution.

"By any standards, ITV at the moment are in the depths of an advertising recession, the industry is leaderless and there is a possibility of consolidation. Talk about fighting a battle at the bottom of a hill where the two maps join," McNally said.

"This is not the time to simply throw ITV to the wolves. It's a time for reflection about where the public interest lies before any snap judgements are made."

His main concern was that if ministers chose to abandon regulating the market it would lead to domination by a handful of wealthy players."The main worry is of concentrations of power. That's why both in the Lib Dem document and the Puttnam Committee - on which I also served - we come out very strongly in favour of Ofcom being able to apply a plurality test and a public interest test to media mergers," he said.

"What we've said - and for the life of me I can't understand why the government is rushing to judgement on this - if you're setting up this new, wonderful expert organisation surely the first thing you should ask it to do is to see if there are any big mergers that are on the table rather than saying 'these are a done deal, you can't look at them'".

On the issue of dumbing down, he argued that politicians should protect the content of the media and rejected the arguments of media firms that they had no right to step in.

"I don't think politicians can be schedulers or programme commissioners. What they can do is create a framework but the framework must encourage the best to prosper," he said.

"If you create a free for all which does allow for cheap and cheerful and dumbing down then you are going to end up with a 24-7 television which is filling in the gaps between the adverts."

He argued that the BBC could be the quality benchmark for the industry and that mass entertainment could meet a quality threshold.

"I do accept the argument that people will seek out the West Wing or even The Simpsons. Quality is not high brow. Quality can be good, popular television.

"I don't want a framework where we have a kind of nanny state but I do want to encourage particularly a strong BBC that can be a benchmark for the other broadcasters. Perhaps in the same way Channel 4 was at its inception," he said.