NTL will make its submission to regulator Ofcom this week, contesting BSkyB's recent £940m raid on shares in takeover target ITV.
Lawyers for the cable group are also understood to be putting together a submission to the Office of Fair Trading under the Enterprise Act.
NTL's grand dreams of a merger with ITV took a blow earlier this month when BSkyB, which is 39% owned by Rupert Murdoch's News Corporation, snapped up a 17.9% stake in the broadcaster.
Just days later ITV turned down NTL's £4.7bn takeover approach as too low and lacking strategic sense.
Leading NTL shareholder Sir Richard Branson lambasted BSkyB's move as a bid to influence ITV and said the swoop had "damaged the plurality of the British media".
The entrepreneur said last week that if ITV were added to Mr Murdoch's media empire "you have let go of democracy and may as well let Murdoch decide who is going to be prime minister."
Veteran film producer and Labour peer Lord Puttnam has also condemned BSkyB's near 20% stake in ITV and called on politicians to take a stand.
"MPs of all parties who have an interest in the future of our democracy should be deeply concerned about every aspect of media consolidation," he said. "At present, with a few notable exceptions, their silence only displays their ignorance, or possibly their sense of quiet shame - take your pick."
NTL - which will rebrand as Virgin Media next year - hopes Ofcom and the Office of Fair Trading will find fault with BSkyB's stake-building.
Ofcom last week formally invited ITV and BSkyB for their opinions as to whether BSkyB's acquisition marked a "change in control" that might affect ITV's programming and said its inquiry would take six weeks. The OFT will examine the implications of the swoop on competition in the TV market.
It is not yet known whether NTL will come back with a higher offer, but market talk is that buying of ITV shares by investors such as fund manager Fidelity and insurer Aviva suggest another bid could emerge at some point.
Pan-European broadcaster RTL is reportedly interested in ITV and its chief executive, Gerhard Zeiler, has said he does not rule anything out. There is also speculation private equity bidders, who have approached ITV in the past, could return to the fray.
The bid talk is against a backdrop of falling ratings and a tough advertising climate at ITV, which has been without a chief executive since Charles Allen's departure almost four months ago.
But interviews with top candidates could happen as soon as this week, according to a source familiar with the situation.
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