Nama's former advisor in the North, Frank Cushnahan, has for the first time declared that he never had any "meetings, dealings, correspondence or contact of any kind" with the US investment group Cerberus or any of its representatives.

Mr Cushnahan, who was a member of Nama's Northern Ireland advisory committee for a three-year period from 2010, has broken his silence to make contact with the Stormont inquiry investigating the sale of the agency's assets in the North.

A solicitor representing Mr Cushnahan has sent a five-page letter to the chairman of the Committee for Finance and Personnel, Daithi McKay, in which he details why the former advisor is "alarmed" both by the evidence given by the Belfast property developer Gareth Graham earlier this month and its future plans to hear evidence from a "political blogger".

Mr Graham shared what the committee at the time described as "extraordinary testimony" during which he revealed he had hundreds of hours of recordings of telephone calls made by Mr Cushnahan while he had used one of the Graham family offices.

The property developer told the inquiry the recordings revealed to him an “ingrained culture of inappropriate and quite possibly illegal business conduct which stretches across political, legal, banking and accountancy sectors”.

Mr Cushnahan had previously been chairman of the Graham family’s bookmaker chain and also a director of Gareth Graham’s property companies.

Mr Graham alleged that when the business relationship broke down with Mr Cushnahan, he became “intent” on destroying the business and that his subsequent appointment to Nama’s advisory board had “directly impacted” [Mr Graham’s] property companies.

Mr Graham is currently involved in a legal battle with Cerberus – the American investment company which bought Nama’s Northern Ireland portfolio for an estimated £1.2 billion – over its plans to place another two of his companies into administration.

In the letter sent by his solicitor to the inquiry's chairman, Mr Cushnahan steadfastly rejects the allegations made by Mr Graham but states that he himself is "not in a position to consider any invitation to appear" before the inquiry until a criminal investigation also underway by the UK's National Crime Agency is concluded into the sale of Nama's former assets in the North.

However, in the interests of providing "some clarity", his solicitor states that Mr Cushnahan has instructed him to explain that he was a former friend and business advisor to the late Sean Graham – Gareth Graham's father – and was also friendly with his mother Brenda.

Mr Cushnahan acknowledges in the letter that the family provided him with an office in Belfast to work from and permitted him to use a telephone there.

But his solicitor states: “At no time was Mr Cushnahan ever informed that his telephone calls would be recorded. Illegally, it now appears that his calls were subject to recording. Many of these calls deal with all aspects of Mr Cushnahan’s professional and personal life”.

He also adds that Gareth Graham has no proprietary right to the tapes or their content and that he has not sought permission from Mr Cushnahan to listen to tapes or to divulge their content or to disclose their content to any third party including any lawyer, journalist or politician.

In the letter Mr Cushnahan also refutes claims made by Mr Graham at his evidence giving session that while he was an advisor to the agency – and contrary to its rules – he also had a potential beneficial interest in a firm that was in the Nama portfolio in the North, chiefly Mr Graham’s companies.

The letter outlines that, with respect to Mr Cushnahan, “no conflict of interest ever arose subsequently that required any form of disclosure to Nama or any third party”.

He also claims in the correspondence that he was at no time ever involved in deciding which loans should be placed in Nama.

The letter not only deals with his alarm over Mr Graham’s evidence to the Stormont committee but also his concerns about who the inquiry is next due to hear evidence from.

The committee has agreed to invite Jamie Bryson, the loyalist blogger and flag protester, who has made allegations on his blog about the sale of Nama's assets in the North, to give evidence in public.

Mr Bryson, who earlier this year received a six-month suspended prison sentence for taking part in unlawful public processions in the North, has said he will "fully respect the committees guidelines and terms of reference".

But through his solicitor, Mr Cushnahan has raised his concerns that the inquiry is prepared to take evidence “from a political blogger who has made false and sensationalised claims on his blog about many third parties”.

“Our client wishes to know what steps the assembly and you are taking as chairman of the finance committee to ensure that this individual is not given a platform to extend his unsubstantiated claims,” the letter states.

The Northern Ireland Finance Committee is scheduled to meet on Wednesday to consider the next steps in its inquiry into the sale of Nama's former Northern Ireland assets.