Mr Diamond was one of scores of current and former Barclays' employees who wanted anonymity during preliminary hearings of a High Court case relating to the manipulation of the London Interbank Offered Rate (Libor), legal papers showed.
The application was dismissed by Mr Justice Flaux.
Lawyers involved in the litigation yesterday released a list of those seeking anonymity in the wake of the judge's ruling.
The list included the names of Mr Diamond and another former Barclays' senior executive, Jerry del Missier.
Mr Justice Flaux said more than 100 people had asked to be anonymised – and lawyers released a list containing 104 names.
The judge said not all those listed were thought to have been involved in any impropriety.
He said more than 20 were on a shortlist of people believed to have been referred to in "notices in respect of Libor".
The emails of others had been provided to regulators investigating alleged Libor manipulation.
Mr Diamond resigned as Barclays' chief executive in July 2012 in the wake of the rate-rigging scandal.
He stepped down after Barclays was fined £290 million by UK and US regulators for manipulating Libor, the rate at which banks lend to each other.
Several firms are airing grievances against Barclays in litigation which Mr Justice Flaux described as a "test case".
A spokesman for Barclays said: "This started as an alleged mis-selling case which the bank considers has no merit. The addition of a claim based on what happened with Libor does not change the bank's view.
"The fact that someone's documents were reviewed by the bank during its review of millions of documents does not mean that such a person was involved in any wrongdoing."
Mr Justice Flaux said a trial was due to take place in London later this year.