The Smithwick Tribunal has decided that the State will pay almost all of the legal costs incurred by one of its most controversial witnesses, former detective garda Owen Corrigan, according to documents seen by RTÉ's This Week.

The tribunal, which examined alleged garda collusion with the IRA, had proposed earlier this year that the taxpayer should not pay costs to Mr Corrigan.

In his final report last November, presiding judge Mr Justice Peter Smithwick described Mr Corrigan as evasive, vague, inconsistent, self-serving and not credible in his evidence.

However, the Tribunal did not find that Mr Corrigan or two other former garda sergeants, Finbarr Hickey or Leo Colton, had colluded with the IRA in the killing of two senior RUC officers, Chief Supt Harry Breen and Supt Bob Buchanan.

The tribunal discussed Mr Corrgian's cost application at a special meeting in January, at which time it emerged that the tribunal had written to his legal team telling them that it was "not minded" to pay his costs.

At that meeting, the tribunal's senior counsel Justin Dillon said that the proposal was related to what was described as Mr Corrigan's "point blank and unambiguous refusal" to provide full details to the tribunal in relation to his bank accounts and his full financial affairs.

Mr Corrigan had told the tribunal that there was no chance he was going to hand them over his bank details.

The tribunal wrote to Mr Corrigan saying to the effect that as a consequence of his failure, it had proposed "he shall not have the costs borne by the taxpayer", that meeting was told.

However, the tribunal's proposal prompted a flurry of legal activity.

Mr Corrigan's legal team responded to the tribunal and argued that if the tribunal had, in effect, already made up its mind at that time to deny him costs, it would be indicative of bias.

Lawyers for Mr Corrigan had threatened to take a case to the High Court.

Mr Justice Smithwick denied at that time that any decision was already made or set in stone relating to Mr Corrigan's costs, despite the proposal contained in correspondence.

He has now decided to award most of Mr Corrigan's costs.

According to confidential tribunal correspondence seen by RTÉ's This Week, Mr Justice Smithwick authorised the payment of most of Mr Corrigan's legal costs in a formal "Order for Costs" which was signed off by the Registrar of the Tribunal, Derek Mills, on 7 April.

It authorised that the State should cover the costs of Mr Corrigan's solicitor and two barristers.

The actual payment falls on the Department of Public Expenditure and Reform.

The costs order covers the vast majority of Mr Corrigan's legal and related costs since he was first granted legal representation by the tribunal on 16 October 2006.

However, the tribunal has decided that it would not authorise the payment of costs relating to one discovery order, which the tribunal sought in May 2013.

The Smithwick Tribunal was set up by the government in 2005 in response to "suggestions" of collusion between members of the garda based in Dundalk and the Provisional IRA, leading to the assassination of two RUC officers, Chief Supt Harry Breen and Supt Bob Buchanan, in an IRA ambush in south Armagh in 1989.

On the whole Mr Justice Smithwick said he believed there had been collusion between gardaí and the PIRA linked to the killing of the two RUC officers.

However, the judge said he could not find any credible information to link any of the named gardaí, including Mr Corrigan, who came to the tribunal's attention, to any act of collusion with the PIRA.

Meanwhile, former communications minister Michael Lowry told RTÉ's This Week that the decision in the Corrigan case would be closely examined by his legal team "with interest".

Mr Lowry is taking a High Court action against the Moriarty Tribunal over its decision to deny him two-thirds of his legal costs at that inquiry.