The Liberal Democrats have taken their battle to force ITV to include Jo Swinson in its leaders' debate to the High Court.
The party has launched a bid for a judicial review of the decision, claiming the broadcaster has excluded Remain supporting voices.
The debate will feature a head-to-head between Labour leader Jeremy Corbyn and Boris Johnson.
Mr Swinson had said earlier in the week that her party would take legal action if ITV did not include her in the debate, scheduled for 19 November.
Outside the Royal Courts of Justice, Liberal Democrat Party President Sal Brinton said: "The TV debates offer the only chance for people to see how leaders compare to each other directly, in a neutral, equal and balanced format. For many people this is the moment they decide how they will vote.
"So it is vital for our democracy to have both sides of the Brexit debate represented at the top table of the Leaders’ debates.
"The Liberal Democrats , on behalf of all those who want our democracy to remain fair and balanced, are legally challenging ITV to do the right, fair and balanced thing.
"We need to preserve the health of our democracy, for this generation and the next."
