Convicted drug dealer John Gilligan has lost his appeal against the imposition on him of consecutive sentences for offences he committed while in prison.

Gilligan, who is due to be released from Portlaoise prison tomorrow, had claimed the sentences were disproportionate and unconstitutional.

The Supreme Court ruled today that a consecutive sentence is designed to mark the gravity of a situation where a prisoner, while serving a term of imprisonment, commits another offence.

The ruling does not mean Gilligan will spend any more time in prison.

The case was the latest in a series of legal challenges by Gilligan.

It related to three offences he committed while serving a 20-year sentence for drugs offences.

He assaulted a prison officer and was twice caught with mobile phones. He was given consecutive sentences upon conviction.

He claimed that because he had to serve more time in prison he was being discriminated against and that the consecutive sentences were disproportionate and unconstitutional.

However, the Supreme Court rejected those claims.

The court also pointed out that Gilligan had in fact benefitted in court appeals from the principal of proportionality.

It noted his 28-year sentence for drugs offences and five-year sentence for assaulting a prison officer had both been reduced on appeal to 20 and two years respectively.