He has been accused of presiding over a “shocking” and “indefensible” failure in “public sector ethics”.
But sacked NI Water boss Chris Mellor is still entrusted by Government with regulating top hospitals in Britain.
His senior boardroom role on English quango Monitor includes overseeing NHS value for money and governance — two of the issues at the heart of the NIW saga.
London's Department of Health has made clear that Mr Mellor retains its full confidence in his Monitor post.
Asked about his dismissal from NI Water's board, a spokeswoman for the Whitehall health department said: “The Department is aware of this matter, which was brought to its attention by Mr Mellor.
“He remains a member of the Board of Monitor and has always had the confidence of the Department in that role.”
Mr Mellor was axed as NI Water chairman by Stormont Minister Conor Murphy over the company's failure to follow competition and approval rules on contract awards.
He had been NIW chairman for three years and acting chief executive for a 14 month period.
Last week, shock was voiced over the contract failings at a hearing of Stormont's Public Accounts Committee.
Its Chairman Paul Maskey said: “Since our committee was established, I don't think we've dealt with a more serious case of complete disregard for public sector ethics.”
Department for Regional Development (DRD) permanent secretary Paul Priestly spoke of being “let down by the board and the executives in Northern Ireland Water”.
He also used the words “shocking, indefensible and unacceptable” to describe the case.
MLAs heard that the rules had not been followed in 73 NIW contracts, worth £28.4m in total.
A lack of competition when awarding contracts left NI Water unable to demonstrate value for money.
Mr Priestly was asked during the Assembly hearing for details of other public positions held by Mr Mellor.
He is deputy chair of London-based Monitor, which describes its role as regulating NHS foundation hospitals to ensure they are “well led and financially robust so that they are able to deliver excellent care and value for money”.
Mr Mellor's role on Monitor includes membership of its audit committee.
His 2003 departure from English company Anglian Water Group was also raised during the Stormont committee hearing.
It was confirmed that officials here were aware of media reports that Mr Mellor had been dismissed as AWG chief executive, when he was appointed NIW chairman.
MLA Mitchel McLaughlin also asked for confirmation that “reference checks” had been carried out.
Asked about these comments, Mr Mellor yesterday told this newspaper: “My resignation from AWG plc in March 2003 was well reported at the time and is a matter of public record.
“DRD were well aware of this and I would point out I was appointed for three years by the normal appointment process for posts like this.
“I would also point out that at the end of my first three-year term as chairman of NIW I was reappointed for four years by Minister Murphy, who told me personally ‘it was well deserved'.”
Mr Mellor had left AWG after a major purchase deal for a construction company proved less than successful.
His departure from AWG is described as a retirement on his profile on the Monitor website.
According to Press reports at the time, Mr Mellor received a £350,000 compensation deal from the English water company and was also entitled to a £150,000-a-year pension.
As chairman of NI Water, he was paid £70,500 in its first year of operation, 2007-08.
His salary in the following year climbed to £159,000, because he also held the acting chief executive post for several months.
He was reappointed chairman of NIW by Conor Murphy for a further four years in April last year, but was dismissed 11 months later.
Mr Mellor receives £15,000-£20,000 a year as a Monitor board member.