Leo Varadkar personally signed off on a plan to give former Taoisigh special supports including VIP airport facilities, increased use of State cars and the salary of a full-time secretary just four months after he took office.
Mr Varadkar was told the decision would cost up to €300,000 a year if all Taoisigh took advantage of the entitlements.
The move took place in October 2017; Mr Varadkar had only taken up office in June.
Former Taoiseach Enda Kenny initially removed the perks, saying in the Dáil at the time: «Former Taoisigh are having their staff and phone entitlements withdrawn with effect from January 1, 2012.»
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The document, obtained under FoI, explained the system of supports for former Taoisigh had been introduced in August 2001 but discontinued in March 2012.
«It would seem reasonable that a former Taoiseach should have access to supports (administrative and otherwise) to support him/her carrying out aspects of work associated with his/her former role which remain after [their] period in office has ceased,» it said.
The memo said that the estimated cost of reintroducing the scheme would be «in the region of €300,000» if all former Taoisigh availed of it.
«The funding requirement can be met within existing resources,» it said.
In putting forward the proposal, the memo said that other countries had much more generous regimes in place for former prime ministers.
In the UK, former leaders can draw down a «public duties cost allowance» worth around €130,000 per annum to help fund an office and secretarial support.
In Australia, office space, phones, printing services, a car and limousine travel for official events are available, while in New Zealand, ex-PMs are entitled to «unlimited free domestic flights, a chauffeur-driven limousine or a self-drive car, with a new car provided every 60,000km».
The reintroduced scheme in Ireland would offer support in six areas, according to the memo.
VIP airport facilities would be provided «prior to departure and on landing». It said this would match what was available to the Taoiseach and former presidents.
The memo said: «[They’re available] as part of a standing arrangement between the department… and the Dublin Airport Authority. It is proposed to extend these facilities to former Taoisigh.»
Support when travelling abroad would also be made available, although details of what this would involve are scant in the documents.
If a former Taoiseach needed help when travelling abroad «to carry out aspects of work associated with his/her former role», they would be put in touch with the local embassy or consulate to receive «appropriate supports».
Transport arrangements for former Taoisigh were also to be enhanced as part of the plan. The former leaders were already entitled to transport to and from «important State functions» but this was to be extended to up to five other events associated with their former role during a calendar year.
The most costly part of the proposal was the provision of secretarial support to help the ex-Taoisigh with aspects of work linked to their old role.
«Salary costs will be met by the Department of the Taoiseach up to the maximum of the higher executive officer… scale (currently €55,329).»
The ex-Taoisigh would be allowed to recruit, select and appoint their own assistant and would be allowed to invoice for the costs of using a recruitment agency to find someone suitable.
However, the secretarial assistant is prohibited from engaging in «constituency or active party political work», according to the memo.
A liaison officer for the former Taoisigh would also be appointed, who could act as «a single point of contact» for all requests for support.
This would include the provision of briefing and/or research material on the government’s policy position on issues of public debate.
The memo was sent to Leo Varadkar on October 23, 2017, by the department’s Secretary General Martin Fraser with a handwritten note saying: «For your approval.»
A day later, the Taoiseach signed off on it with a single word: «Approved.»
In a statement, a department spokesman said: «Former Taoisigh receive support in carrying out work associated with their former role which remains after their period in office has ceased.»
He added: «It is entirely a matter for each individual former Taoiseach as to whether they avail of any supports.»