OPPOSITION parties have called for an immediate inquiry into how the chief witness in a major gangland trial was threatened by armed gunmen while under round-the-clock garda protection.

Calling for an urgent review of the witness protection system, Green Party justice spokesman Ciarán Cuffe said gardaí had proven unable to keep track of witnesses whom they are supposed to be protecting, putting the safety of the witness and the integrity of the trial in jeopardy.

Fine Gael has also called for an urgent review of the witness protection system, with justice spokesman Jim O'Keeffe demanding formal legislation to deal with the protection of key witnesses.

The comments come after the Sunday Tribune revealed that the chief witness in the trial against an alleged gangland figure was able to evade her garda minders and travel to London, where she was targeted by armed men.

Christine Mahon from West Dublin subsequently withdrew her statement to gardaí implicating Declan Curran, 24, from Cardiffsbridge Avenue, Finglas, in the murder of Willie O'Regan at the dead man's Cabra flat in 2003.

The trial against Curran collapsed after Mahon retracted her initial statement to gardaí, with prosecuting counsel claiming she had been terrified into changing her evidence.

Mahon denied the suggestion.

According to Ciarán Cuffe, "we are very concerned that this case illustrates that gardaí are not able to keep track of important witnesses. That raises a lot of questions in relation to the safety of the witness, the integrity of the case and the likelihood that evidence can be affected by intimidation."

Sources in the Department of Justice expressed concern over the garda failure to track the movements of Mahon.

However, they added that there is no legal means by which the state can place a witness into a 'safe house' involuntarily, as is the practice in other jurisdictions.

Following the collapse of the murder trial against Limerick youth Liam Keane last year, justice minister Michael McDowell announced moves to change the admissibility of evidence. Under the new proposals, retracted statements will be allowed in court.

Speaking to the Sunday Tribune, junior justice minister Willie O'Dea said the use of retracted statements will go a long way towards guaranteeing that trials that may have collapsed after witness intimidation may now continue.

However, the Green Party said this did not obviate the need for effective witness protection. "We should be able to avoid a situation in the first place where people feel compelled by fear to retract their statements", said Cuffe.

Jim O'Keeffe also criticised the witness protection system.

"It is no longer good enough that it is run on an ad hoc basis, " he said.