The Financial Conduct Authority has been ordered to disclose additional documents after a former UBS trader lodged a complaint against the regulator with the Upper Tribunal.
In January this year, the FCA ruled that Arif Hussein, a former derivatives trader at UBS in London, should be banned from providing financial services.
The regulator claimed Mr Hussein informed GBP trader-submitters of his preferences for GBP Libor rates, "while closing his mind to the risk" that these figures would be used to manipulate Libor.
But in an application to the Upper Tribunal, Mr Hussein requested the FCA be forced to disclose regulatory proceedings with another UBS trader, Panagiotis Koutsogiannis, claiming they were relevant to his own case.
Judge Timothy Herrington agreed, calling on the FCA to "make further disclosure in relation to evidence before the RDC [Regulatory Decisions Committee] in respect of Mr Koutsogiannis’s regulatory proceedings".
The judge also ruled in favour of an FCA application to strike out four paragraphs of Mr Hussein's reply.
In 2012, the FCA fined UBS £120m following an investigation into its role in the Libor scandal.
The FCA stated in its final notice: "There was a culture where the manipulation of the Libor… setting process was pervasive. The manipulation was conducted openly and was considered to be a normal and acceptable business practice by a large pool of individuals."
Libor is considered one of the most important interest rates in finance, affecting $450 trillion (£363 trillion) of transactions worldwide, according to figures in the Wheatley report from September 2012.