A BBC programme wants to name an MI5 agent because he represents a danger to other women and must be publicly identified to prevent future harm, the High Court has heard.
The BBC has gone to court to try and stop an injunction against a report that would identify an MI5 agent.
The BBC report says the agent used his status to abuse two ex-partners - and naming him is in the public interest.
But the government says identifying him risks his life and national security.
The legal battle is over whether the BBC can air a news story about a male MI5 informant known only in the court proceedings as "X".
If aired, the BBC's news report would claim that X used his status as an agent to abuse, control and coerce a former partner, referred to by the pseudonym "Beth" - and that MI5 either knew or ought to have known about this and was wrong to use him as an agent.
Another woman who alleges she was abused by him - known by the pseudonym "Ruth" - has said she fears X will kill a woman if he is not "challenged and exposed".
The government's Attorney General Suella Braverman is seeking an injunction to block the broadcast, arguing that identifying X would create a "real and immediate risk" of serious or life-threatening harm to him and would damage national security.
The case is being held over two days at the High Court by judge Mr Justice Chamberlain.
'Must be named to warn others'
On Tuesday, on the first day of the hearing, lawyers representing Ms Braverman said that she "neither confirms nor denies" the BBC's claim that X is an agent or covert human intelligence source (Chis), but is conducting the hearing on the "hypothetical assumption" that he is or was.
The BBC's legal team told the court: "Beth and Ruth have an intimate insight into X's psyche and behaviour, making them uniquely placed to evaluate the risk that he poses to other women."
Lord Pannick, representing the broadcaster, said: "He told one of those women, who we call Beth, that he worked for MI5 in order to terrorise her, in order to control her. The programme will say that MI5 should have known about his behaviours and realised that it was not appropriate to [have] used him as a Chis."
He told the court there is a "particularly strong public interest" in the story given the "current context of public debate" on coercive control of women by male partners.
And there is "simply no cogent evidence to justify a conclusion that X is at serious risk of serious harm or death" if he is identified, Lord Pannick said.
In a witness statement, Beth said: "I think X is a very dangerous individual - to me, to ex-partners and to other women. He thinks it's okay to treat women the way that he's treated me. I believe he must be named and identified to the public at large to warn others."
Ruth said in a statement: "I consider that he is dangerous enough to kill a woman and I fear that he will do so if he is not challenged and exposed. I think it is crucial that other women know his identity and what he looks like, so that he cannot trick and harm them."
'Damage national security'
But Sir James Eadie QC, for the Attorney General, said: "Publication of the report would constitute a breach of confidence/false confidence by the BBC.
"To do so would damage national security and the public interest. It would also create a real and immediate risk of serious or life-threatening harm to X."
He said that there are "avenues for complaint and investigation" in relation to any allegations against MI5 - and that the "most serious" allegations against X have been investigated by police and no further action was "considered appropriate to be taken".
He added: "The case of wrongdoing by X, and the subsequent speculation that MI5 must have been aware of it and failed to react appropriately, rests on foundations that are anything but solid.
"There is real doubt about the reliability, credibility and motivation of Beth. Police and the Crown Prosecution Service have been involved but the outcome has been no action - in significant part because of those doubts."
The Attorney General says there is no objection to a broadcast about the allegations against X and MI5's use of agents which does not identify him, but argues that identifying him would be a breach of confidence and infringe X's human rights.
Mr Justice Chamberlain told the court earlier on Tuesday that reference to "agent" in the case meant "covert human intelligence source", which refers to someone who is "not a member of MI5" but more of an informant.
The hearing will continue on Wednesday but will largely be in closed proceedings.