The Public Accounts Committee is to ask the Attorney General whether a whistleblower should be allowed to attend for a public hearing.
The call comes after the PAC was given two conflicting sets of legal advice about whether the whistleblower is covered under new laws.
Civil servant Gerry Ryan has raised allegations of tax evasion by politicians, thinking he was protected under the new laws.
Chairman John McGuinness said it was important the PAC resolves the problem once and for all.
"It's unfair to Mr Ryan to leave a stand-off between one piece of legal advice and another," he said.