The chief executive of the National Asset Management Agency (Nama) has asked the Garda Commissioner to investigate new allegations made by Independent TD Mick Wallace, including that a construction firm paid a bribe to exit the agency.

Under parliamentary privilege in the Dáil on Wednesday Mr Wallace said the manager of a portfolio in Nama told a construction firm looking to exit the agency that “it will cost you €15,000 in cash and I want it in a bag”.

He said the construction firm paid the money and a few weeks later “he demanded the same again. They duly obliged and all was sorted.”

In a statement Nama said the allegation that an employee had demanded and accepted a bribe “cast a shadow over all Nama officers”.

Later in the Dáil, Mr Wallace raised 20 questions on the controversial Project Eagle sale, which has been described as the largest property sale in Ireland's history.

During a debate on Northern Ireland, Mr Wallace questioned the sale of the Northern Ireland loan portfolio of 850 properties; the role of Frank Cushnahan, formerly a member of Nama’s Northern Irish advisory committee; and Minister for Finance Michael Noonan’s knowledge of the sale.

Nama chief executive Brendan McDonagh has written to Garda Commissioner Noreen O’Sullivan requesting she investigate Mr Wallace’s claims.

Mr McDonagh added said Mr Wallace had not provided the agency with any information relating to his comments in the Dáil.

“The allegation, if not investigated as a matter of urgency, casts a shadow over all NAMA officers and, accordingly, we will ask that the Deputy’s allegation, including any evidence that he may claim to possess, be investigated as a matter of urgency.”

A spokesman for Nama added that under Section 19 of the Criminal Justice Act 2011, any party with evidence of criminal wrongdoing was legally obliged to bring such evidence to the attention of the gardaí.

“In event that deputy Wallace is aware of such evidence and has not brought it to the attention of An Garda Síochána, this may be a breach of Section 19.”

Mr Wallace also claimed judges, barristers, solicitors and top four accountancy firm partners were in Nama but their personal guarantees had not been enforced by Nama.

The Independent deputy also asked in the Dáil what role the former secretary general of the Department of Finance John Moran had played in Nama’s handling of a particular portfolio, which he claimed Mr Moran was “unnaturally interested in playing a significant role in”.

Taoiseach Enda Kenny responded: “You’re making allegations and assumptions in the middle of which you say you have facts. You have a duty to bring those allegations, assertions or facts to PAC, which has full authority to follow through”.

Nama also described as “categorically false and incorrect” Mr Wallace’s assertion in the Dáil that the agency was aware since January of £7 million being placed in an offshore Isle of Man account by a Belfast solicitor.

At a Public Accounts Committee hearing last week, Nama chairman Frank Daly said the first he had become aware of that issue was when Mr Wallace had disclosed in the Dáil a fortnight ago.

During Leaders Questions o0n Wednesday Mr Wallace made four new allegations relating to Nama.

He alleged the agency had not acted to enforce personal guarantees against prominent barristers, judges, accountants and bankers associated with property syndicates assembled by wealth management companies.

“Nama is responsible for some people being tossed out of their homes but it looks like some of the great and good of Irish society are blessed with Nama’s good will,” he said.

He questioned the role former secretary general of the Department of Finance John Moran had played in Nama’s handling of a particular portfolio.

Separately, the Belfast law firm Tughans on Wednesday rejected claims by its former managing partner Ian Coulter concerning a bank account which contained £7.5 million and which has been the subject of allegations relating to the purchase of Nama’s former portfolio in the North.

Tughans said it disputed Mr Coulter’s assertions he personally informed the law firm about the account and voluntarily transferred the money from the account to the firm last December.

Instead the Belfast firm said: “Tughans strongly disagrees with Ian Coulter’s version of events surrounding the treatment, discovery and retrieval of the professional fees and his exit from the practice and it has passed all documentation relating to this to the Law Society.”

“Tughans voluntarily brought the matter to the attention of the Law Society and will continue to co-operate with any inquiry.”