The Liberal Democrats are launching a legal challenge against ITV over its decision to exclude their leader from the channel's election debate.
ITV is hosting a primetime head-to-head between Conservative leader Boris Johnson and his Labour counterpart Jeremy Corbyn on 19 November.
But the Lib Dems' Jo Swinson has not been invited to participate.
Their party president Sal Brinton said the decision "disrespects" those who voted Remain in the Brexit referendum.
Speaking outside the High Court in London after filing for a judicial review, she added: "People know more about where they stand on Brexit than for which party they will vote for.
"So it is vital for our democracy to have both sides of the Brexit debate represented at the top table of the leaders' debates."
When ITV announced its plans, the channel said it would hold a live interview-based programme alongside the leaders' head-to-head to allow other parties to comment, as well as another multi-party debate ahead of the 12 December poll.
But Ms Swinson said it was wrong to exclude "a voice of Remain" and the only woman who could be the next prime minister.
The BBC has also announced a debate between Mr Johnson and Mr Corbyn as part of its coverage in the run-up to the general election, which has also prompted criticism from the Lib Dems.
Ms Brinton told reporters it was too early to say whether the party would also launch a legal challenge against the BBC over that decision.