Eurosceptic campaigners from the Vote Leave group have voiced anger over a planned ITV pre-referendum programme featuring David Cameron and Nigel Farage.
They say they want to see a Tory Eurosceptic to face the Prime Minister instead of the Ukip leader - and have threatened to involve the media regulator.
ITV News political correspondent Carl Dinnen reports:
Culture Secretary John Whittingdale has said he does not think ITV's Cameron-Farage EU referendum event is "fair" - and urged Vote Leave to lodge a formal complaint with Ofcom.
Speaking to ITV News' national editor Allegra Stratton, Mr Whittingdale said if campaigners felt the line-up for the June 7 broadcast was "unbalanced" then they ought to complain.
It comes after Vote Leave criticised the broadcaster for featuring a Q&A event with David Cameron and Nigel Farage, instead of somebody from the official Vote Leave campaign.
"If I they think that this is unbalanced, and I have to say it does not look fair to me, then yes they should certainly make a complaint," he said.
"But I'm not speaking as Secretary of State, I'm speaking as somebody who supports the Vote Leave campaign.
"I do think it looks very odd if the representative of the argument for leaving is not somebody from the official campaign, and therefore I think the official Vote Leave campaign would be entitled to make that point to a regulator."
ITV has hit back at claims of a "stitch up" in staging a head-to-head event between Nigel Farage and David Cameron before the EU referendum.
The official Vote Leave campaign has threatened legal action, accusing the broadcaster of allowing the Prime Minister to hand-pick Mr Farage as his opponent in an attempt to sway voters, and said it had given more air-time to 'in' campaigners.
But the TV giant said it had made an "editorial decision" in asking Mr Farage to appear in the Q&A show on June 7, as he had been a "leading proponent" of Britain leaving Europe for more than two decades.
In a statement, 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 on June 9 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 June 7 programme; the PM called the referendum, and the country wants to hear from him, and Nigel Farage has been a leading proponent of an exit from the EU for more than 20 years and his party received 3.8 million 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.
The culture secretary and Leave campaigner John Whittingdale has described ITV's decision to pit David Cameron against Nigel Farage in an upcoming debate on the EU referendum as "very strange".
He was speaking to ITV News after the Vote Leave campaign threatened to take legal action against the network, which it said has allowed the prime minister to pick his own opposition.
Mr Cameron, who wants Britain to stay in the EU, should debate the representative of the official Leave campaign, a statement said.
Mr Whittingdale told ITV News that in his personal view: "I do think that ITV's decision to have the Prime Minister debate somebody who isn't from the official organisation campaigning for Britain to leave [the EU] does look very strange."
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An upcoming head-to-head EU referendum debate to be broadcast on ITV has been manipulated by the Government "to give itself every possibly advantage", according to the Leave campaign.
Vote Leave said the rules of the televised debate between David Cameron and Ukip leader Nigel Farage - scheduled for June 7 - were "being set" by the Government.
The latest claim comes after Vote Leave, accused of "excluding" Mr Farage from their campaign, threatened legal action against ITV on Wednesday.
"ITV has accepted the Prime Minister's demands without even discussing it with the official campaign and has allowed the Prime Minister to dictate his own opponent", a statement read.
"Since the campaign began, ITV has also given twice as much airtime to the IN campaign than to the Leave campaign.
"We think that the Prime Minister ought to debate the representative of the official Leave campaign.
"In a serious democracy, the Government should not be allowed by a free media to pick its own opponents in the official debates on the most important political decision in decades".
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Vote Leave are trying to "exclude" Nigel Farage from their EU referendum campaign, Ukip claims.
The Ukip leader is set to go head-to-head with Prime Minister David Cameron in the first in-out debate live on ITV on June 7 - but this is being threatened with legal action by Vote Leave.
A Ukip spokesperson described this as an attempt at "excluding" Mr Farage from their campaign.
"It is deeply disappointing that rather than rallying behind Nigel Farage for what will be the biggest one-on-one debate of the referendum campaign, Vote Leave are instead threatening court action to stop Nigel from taking on the Prime Minister", the spokesperson said.
The statement added: "This referendum is bigger than the Conservative Party and bigger than party politics.
"It is about the very future of our country and this ITV debate will reflect that.
"All on the Leave side must put their egos to one side and support Nigel as he prepares to take on the Prime Minister in what will undoubtedly be the defining moment of the referendum campaign".
A source from the Vote Leave campaign said: "This is an outrage.
"ITV admitted to us that the only reason they were asking for Nigel Farage was to secure the Prime Minister.
"They are allowing Number 10 to choose their opposition. This is because Number 10 are refusing to debate leading Vote Leave figures.
"ITV have effectively become part of the 'In' campaign. We will take them to court and we will win."
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