Former UUP leader Steve Aiken was reported to the PSNI by a Stormont standards watchdog for allegedly failing to cooperate with a misconduct probe.
Mr Aiken had been invited for interview several times by the Assembly standards commissioner Dr Melissa McCullough but he did not respond.
She made a formal complaint to police who submitted a file to the Public Prosecution Service.
The PPS decided not to pursue a case, saying the evidential test for prosecution had not been met.
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In her report to an Assembly committee, Dr McCullough said it is a "criminal offence" under Stormont legislation to fail to attend an interview under notice.
She said the South Antrim representative, who is seeking re-election in May, had "failed to behave in a way that is consistent with the Seven Principles of Public Life".
Mr Aiken strongly denied failing to cooperate with the commissioner, blaming a delay in responding on the Twelfth of July holidays.
It follows a complaint made against Mr Aiken to the commissioner by Sinn Féin's Maolíosa McHugh alleging breaches of the MLA code of conduct.
In November 2020, Mr Aiken told MLAs at a finance committee meeting that he had made a complaint to the commissioner relating to Mr McHugh.
It followed a controversy over some Sinn Féin offices receiving in error emergency business support grants during the Covid-19 pandemic.
Mr Aiken claimed that Mr McHugh had failed to declare an interest over his office being in receipt of a grant when Stormont officials attended the committee.
The commissioner investigated Mr Aiken's complaint and did not uphold the allegations against Mr McHugh. The Assembly standards committee last year concluded there was no breach of the code.
In her probe into the complaint against Mr Aiken, Dr McCullough said from June 7, 2021, she invited him for interview twice but this "failed to elicit a response".
She then twice issued a formal notice to attend on June 28 and July 7 but the UUP MLA did not turn up. She later made a report to the PSNI.
In a subsequent written statement to the commissioner, Mr Aiken disputed Mr McHugh's complaints, claiming that he was declaring an interest.
The commissioner found Mr Aiken breached the MLA code in relation to disclosing confidential or protectively marked information, and failing to cooperate at all times with the watchdog probe.
The Assembly standards committee proposed that following May's election their successors consider an appropriate sanction for recommendation to the next Assembly.
In a statement Mr Aiken said: "I reject in the strongest possible terms that I failed to cooperate with the commissioner.
"A letter from the commissioner was delivered on the Friday before the 12th of July holidays and was left with the landlord of my constituency office.
"The letter did not reach me until after the proposed date of the meeting with the commissioner. I informed the commissioner of the circumstances immediately upon receipt of the letter.
"The commissioner referred the matter to the PSNI. Upon completion of the investigation, it has been confirmed that no further action will be taken by the PSNI or the PPS."
A PSNI spokesman said: "A 59-year-old man voluntarily attended Newtownabbey Police Station on Thursday 14 October where he was interviewed under caution by detectives investigating allegations of potential criminality in contravention of section 31 of the Northern Ireland Assembly (Independent Financial Review and Standards) Act (Northern Ireland) 2011.
"A file was then forwarded to the Public Prosecution Service for direction."
In a letter to the commissioner in January, the PPS said the evidential test for prosecution had not been met.
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