A Dail ethics watchdog has no right to investigate tax-dodging TD Mick Wallace if his dealings with Revenue predate his time in parliament.
The Members' Interests Committee will look into specific timelines for when the taxman discovered the Wexford Independent had under-declared VAT returns for his construction company.
Chairman Thomas Pringle said the committee has also written to Mr Wallace asking him to authorise Revenue Commissioners to reveal when they reached the 2.1 million euro settlement, to which the TD admitted last week.
"We will be trying to get the information in relation to the timeline as to what took place and be able to make a decision as to whether we have a jurisdiction over this matter," said Mr Pringle.
He said legal advice to the committee was clear that if Mr Wallace came clean and settled with Revenue before he became a TD in February last year, it has no remit to probe.
It is understood Mr Wallace informed Revenue that he had knowingly under-declared how much VAT he owed in 2008 and 2009, as tax chiefs were carrying out an audit investigation into his business MJ Wallace Ltd. But it is unknown when this happened, or when the TD agreed a settlement with Revenue.
The platinum-haired property developer-turned-politician has maintained he is not personally liable for the money and that since the business is insolvent, the funds will not be repaid to the authorities.
As the TD's former construction business was officially named on the Revenue Commissioner's defaulters list on Tuesday, party whips said they would wait for the Members' Interests Committee to make its move before considering passing a motion of censure.
Taoiseach Enda Kenny also said the Government would "stand ready" to issue an all-party motion should that decision eventually be taken. However, Mr Pringle has called on party whips to hang fire on passing a motion of censure for fear of prejudicing a potential investigation.
"If the committee decides that it can investigate this matter, obviously it would be better that there would be no motion of censure put before the House while the committee is processing its enquiries," he went on. If passed, such a motion is a rap on the knuckles and cannot force the TD to resign.