Investigations which led to the controversial tax evasion dossier went on for “too long” and left a “cloud of suspicion” over those who may not have done anything wrong, according to legal advice on the claims.

The dossier, compiled by Gerry Ryan, was sent to members of the Public Accounts Committee last week.

Matthias Kelly QC, a former chairman of the Bar Council in England and Wales, was appointed in 2005 by then minister for enterprise Michéal Martin to examine the claims made by civil servant Gerry Ryan.

In a report on Mr Ryan's work, Mr Kelly said: "Prolonged 'investigations' of this nature may well, in the end, prevent any wrongdoing being prosecuted."

Mr Kelly said Mr Ryan had first started investigations in 1998, with other aspects added in 1999, and said the period up to 2005 was "too long".

“There is a legitimate public interest in bringing them to a conclusion,” Mr Kelly said.

“Those who are suspected of wrongdoing have a right to closure. If they have not engaged in any wrongdoing they are entitled to have the cloud of suspicion removed. If there has been wrongdoing it is in the public interest that it be uncovered and dealt with.”