Former Environment Minister Phil Hogan was informed as far back as December 2012 that Irish Water had allocated a sum of more than €40m out of which consultants, among others, would be paid.
According to a document obtained by RTÉ's This Week programme, Mr Hogan signed and approved of the document on 10 December 2012.
That is more than a year before the controversy broke over the spending of tens of millions of euro on consultancy services during the new water utility's set-up.
Mr Hogan said he did not know that €50m had been spent on consultants when the controversy broke in January of this year.
He expressed concern at the level of spending at the time.
The December 2012 document, which was marked as "confidential", was written by a senior official at Mr Hogan's department and it was brought directly to his attention.
It included an assessment of progress being made,in late 2012, on the set up of Irish Water, and the Government's broader water reform programme.
It make reference to the provision at that time of a sum of €43.5m, out of which Mr Hogan was told that "external consultants" as well as other seconded staff from Bord Gáis and local authorities were set to benefit.
It said the bulk of this cost would be spent on "new systems" including billing and call centre systems, which were essential to get the new utility up and running and ready to charge customers for water.
Mr Hogan did not respond to queries from RTÉ on the document.
It follows a report by RTÉ three weeks ago, which also showed that Mr Hogan signed off on a summary breakdown of Irish Water's €180m spending plans in October 2013, three months before the controversy over the utility's consultancy spend erupted.
Unlike the confidential memo from December 2012, the October 2013 document did not make specific reference to consultants, but it did list the multi-million euro allocations earmarked for new IT and other systems, all of which Irish Water insisted has been understood to include a significant consultant spend.