Jailed real IRA leader Michael McKevitt has lost his High Court case to try secure one third remission of his sentence for good behaviour.

McKevitt (59) from Beech Park, Blackrock in Co Louth is serving 20 years in Portlaoise Prison for directing terrorism and membership of an illegal organisation.

He has done courses in French, music, computers and yoga while on the Republican landing of Portlaoise jail.

He claims he is entitled to one third remission because the prison rules state that by engaging in these 'structured authorised activities', he is less likely to re-offend on his release.

However the justice minister turned down the application by the Real IRA leader to have his sentence shortened, in part because gardaí believe he will re-engage in dissident activity.

Following a challenge the High Court has upheld that decision.

It ruled that the prison rules are not to be applied mechanically without regard to the outcome - because that could lead to absurd results, like embezzlers getting out of jail early for doing accountancy courses.