Tanaiste Leo Varadkar has been accused of giving a "dig-out" to a friend by leaking a confidential document about a GP contract.
Sinn Féin leader Mary Lou McDonald rejected claims the decision to leak the details to a third party were motivated by public interest.
She accused Mr Varadkar of abusing his then position as taoiseach.
Mr Varadkar is to tell the Dáil why he shared the confidential document this afternoon.
In his first public address since the controversy emerged over the weekend, the Fine Gael leader will give a statement on his decision to disclose the document to Dr Maitiú Ó Tuathail.
Dr Ó Tuathail, a friend of Mr Varadkar, is a former president of the National Association of General Practitioners (NAGP), a rival organisation to the Irish Medical Organisation (IMO), which was part of the negotiations.
Ms McDonald told the Dáil: "It was giving a dig-out to a friend, it's as crude as that.
"A friend whose organisation was in competition with the IMO for members, for their subscriptions and for influence.
"An organisation that subsequently collapsed and was liquidated in July 2019.
"It was clear that Deputy Varadkar abused his position as taoiseach."
Putting a series of questions to Taoiseach Micheál Martin, Ms McDonald added: "Can you please tell us, when did the tánaiste inform you he had leaked the document - who gave Leo Varadkar the GP contract document?
"Has Leo Varadkar leaked other documents? You have been very categoric that no law was broken, is that the position of the attorney general?"
Mr Martin repeated his comments that the leaking of the document was "not appropriate" and was "the wrong way to do things".
The Fianna Fáil leader said a lot of details about the GP contact were already in the public following a press release issued by the IMO.
"The essential details were out there but as I have said myself, it should have been published as early as possible," Mr Martin added.
He told the Dáil he asked his general secretary to have a preliminary look for any correspondence between his department and the NAGP.
"The only thing they have found so far is a letter from the NAGP that is dated April 9 ... and they are related to their concern of the removal of medical cards," he added.
Labour's Alan Kelly said it was a "huge issue" that needed to be dealt with.
"The public are drawn back to times of golden circles and the Galway tent and friends in high places," he told the Dail.
"I thought we had moved on.
"There is a bit of time before the tánaiste addresses the house - please go to him and ask him not to use the lame excuse that the reason it was leaked was because he was trying to ensure that the maximum number of GPs were going to take up this contract.
"It doesn't wash.
"This is also about you and your role as taoiseach and how you are going to deal with it, it's about competency and how you will deal with the issue over the next number of hours and days."
The leaked document contained a draft agreement reached between the Department of Health, the HSE and the IMO in April last year.
Mr Varadkar is due to speak for some 20 minutes before taking questions from opposition parties this afternoon.
Fine Gael ministers have rallied to defend their leader over recent days.
Foreign Affairs Minister Simon Coveney said yesterday that Mr Varadkar shared the document to help sell the contract to GPs.
The Standards in Public Office Commission (Sipo) has been asked to investigate the circumstances around the incident in a letter from Rise TD Paul Murphy.
He has asked Sipo to examine the details surround the sharing of the document, which first emerged in the Village magazine's November edition.
