Vote Leave has issued a veiled threat to ITV, warning there will be "consequences" to what the group claims is a Remain bias.
The campaign group has lambasted the broadcaster for scheduling a programme in which David Cameron and Nigel Farage will debate the issue in a programme on 7 June called Cameron and Farage Live: the EU Referendum.
A second live programme will be broadcast two days later, in which it is thought Boris Johnson will appear – but not the Prime Minister.
It is thought Cameron wanted to avoid a "blue-on-blue" debate with fellow Tories.
But Vote Leave has threatened ITV with legal action over the move – while issuing a more vague threat of unnamed consquences further down the line.
A statement attributed to a "senior Vote Leave source" late last night claimed "the establishment" – by which it seems to refer solely to ITV – was "fixing the debates to shut out the official campaign", which Farage is not part of.
The statement said:
ITV is led by people like Robert Peston who campaigned for Britain to join the euro. ITV has lied to us in private while secretly stitching up a deal with Cameron to stop Boris Johnson or Michael Gove debating the issues properly.
ITV has effectively joined the official IN campaign and there will be consequences for its future – the people in No 10 won't be there for long.
Peston – who has recently moved to ITV from the BBC – said it was a "mad slur on me and ITV", initially saying "it must be a practical joke".
He later added: "I can hardly believe I need to say this, I never campaign for the euro & ITV is wholly impartial in EU referendum debate."
So, & I can hardly believe I need to say this, I never campaigned for the euro & ITV is wholly impartial in EU referendum debate
— Robert Peston (@Peston) May 11, 2016
An ITV spokeswoman said: "ITV has not lied to anyone, nor has there been any kind of 'stitch up'. Senior figures from the Vote Leave campaign have been invited to our debate [9 June] and have every opportunity to air their views and opinions on the issues in a two-hour long peak time programme on ITV.
"It was our editorial decision as to who would take part in the 7 June programme; the PM called the referendum, and the country wants to hear from him. Nigel Farage has been a leading proponent of an exit from the EU for more than 20 years and his party received 3.8m votes at the election. We invited them both and they accepted.
"We think our viewers will find both programmes useful in providing information ahead of polling day. Our programming will, as always, be fair, balanced and duly impartial. "