Jeremy Corbyn is asking a court to allow him to personally fight a legal action launched in a bid to overturn the Labour Party's decision to guarantee him a place on the leadership ballot.
A High Court claim brought by Labour donor Michael Foster, a former parliamentary candidate, is currently against one named defendant - the party's general secretary Iain McNicol, who is being sued in a representative capacity.
But Mr Corbyn wishes to be added as a party to the proceedings as second defendant.
His application was heard by Master Victoria McCloud at a preliminary hearing at the High Court in London.
Written argument in support of his application states: "His personal interest in the subject matter of this litigation is pressing and obvious and distinguishes him from the general body of members represented by Mr McNicol."
The case, which is expected to be aired fully on July 26, follows the decision of Labour's National Executive Committee (NEC) that the leader should automatically be included in the contest.
NEC members wrestled with legal advice for six hours over whether Mr Corbyn would need to secure 51 nominations to make it on to the ballot paper after both sides insisted the party rulebook backed their case.
The written document before the court also says that Mr Foster's legal action "seeks, in effect, to reverse this decision so that Mr Corbyn will not be eligible to stand as a candidate in the forthcoming leadership election unless he secures the requisite number of nominations in the time limited by the rules".
Mr Corbyn was not present for Tuesday's hearing. The court heard he had wished to attend but had a number of "pressing engagements".
Judgment will be given at 10.30am on Wednesday.