Garda Commissioner Nóirín O'Sullivan has stepped down from an important internal panel that determines senior promotions within the force.
s O'Sullivan is to be replaced by one of her deputies, Donal Ó Cualáin, on the panel that appoints assistant commissioners.
The commissioner has said she has taken the decision for "work-related reasons".
But sources point out that she must now prepare for the fact that she will be a key witness at the Charleton Inquiry, which is examining the alleged smear campaign against Garda whistleblower Maurice McCabe.
The move to step down from the board was taken this week following communication between the force and the Policing Authority.
Ms O'Sullivan has strongly rejected concerns about her capacity to lead the force while also dealing with the tribunal.
The chairperson of the Policing Authority, Josephine Feehily, said last week it had concerns about her ability to do both.
The commissioner rejected these concerns, saying she had put a team in place to drive planned reforms of the force while also dealing with the needs of the tribunal.
"We are already on record as saying we will fully co-operate with the tribunal in every way, and we look forward to being able to do that," she said.
Referring to vacancies that previously existed at senior management level in the force, she said: "In the last three years I as an individual, as both an interim commissioner of An Garda Síochána and the Commissioner of An Garda Síochána, have had to operate on a very limited capacity, so I am no stranger at having to operate at a limited capacity."
Asked if she was surprised by Ms Feehily's comments, the Commissioner said: "We discussed in detail at both private and public meetings with the authority and at no stage did the authority express anything other than confidence in our capacity to do the job."
Separately, Alan Shatter refused to say if he was aware, when he was justice minister, of false smears allegedly circulated by senior gardaí about whistleblower Sgt McCabe.
Mr Shatter resigned from the cabinet in May 2014, a month after a file was created by Tusla containing a false sexual abuse allegation against Sgt McCabe.
The former TD told the Irish Independent the first he learned of the file was when he saw a report last month on RTÉ.
He said he was "reflecting" on whether he would make a submission to the Disclosure Tribunal, which is investigating the treatment of Sgt McCabe and other whistleblowers by Garda management.
Asked if he had information that would be relevant to the work of the tribunal, Mr Shatter said: "The first I learned of the bizarre conduct of the HSE and Tusla, and I can say this without any fear of contradiction, was when I watched the 'Prime Time' programme. I think Judge Charleton is an excellent judge. I wish him well with the tribunal. I am reflecting on whether there is anything that I might submit to him that would assist him in his work."
Asked if he was aware of any attempts to smear Sgt McCabe, Mr Shatter said: "I am simply not going to get into that today."