Despite insisting in January that he was not aware of the level of spending on outside experts by Irish Water, a new document unearthed by RTÉ shows he personally signed off on a letter confirming the full spending costs for the utility in October 2013.

After it emerged at the beginning of 2014 that almost half the €180m start-up costs for Irish Water — €86m — went on outside consultants, Mr Hogan said he did not know how much was spent on consultants as he did not “micro-manage” the organisation.

However, RTÉ reported it had seen a document detailing the breakdown of spending on services such as IT, customer billing, and economic advice, that the then-minister signed off on October 22, 2013, detailing spending plans for the organisation.

Though the letter did not specifically refer to consultants, it contained spending of €32m on IT, €13m on economic advice, €12m on billing and registration, and €8m on support services.

When asked in January if the scale of spending on outside consultants had been a PR disaster for Irish Water and the Government, Mr Hogan said: “You can’t make an omelette without breaking eggs.”

Fianna Fáil leader Micheál Martin seized on the revelations, stating that Mr Hogan had now been “caught out”.

“We now know from this document, which was signed three months before the controversy broke, that he had seen and approved of the establishment costs, including the consultancy costs of Irish Water,” Mr Martin said.

Sinn Féin leader Gerry Adams said: “It has now emerged that Phil Hogan signed off on the full costs of Irish Water three months before the controversy about the cost of consultants emerged in the public domain.

“Phil Hogan has been caught out. It is clear now that Phil Hogan should not have been nominated for EU commissioner by Enda Kenny,” Mr Adams said.

The fresh controversy comes as some Irish opposition MEPs moved to publicly oppose Mr Hogan’s appointment to a European commissionership. Mr Hogan has emerged as a prime candidate for the key agriculture role within the European Commission.