Mr James Sheehan, the Sinn Féin director of elections in Kerry North, was released last night without charge from Killarney Garda station.
He had been questioned as part of an investigation into an alleged vigilante-style abduction before Christmas.
Gardaí confirmed no charges had been laid against Mr Sheehan, but said a file on the incident was being sent to the Director of Public Prosecutions. Mr Sheehan had been arrested almost 12 hours earlier.
Mr Martin Ferris, councillor and Sinn Féin general election candidate in Kerry North, said in a statement that Mr Sheehan's arrest was "an outrageous interference in the political process".
On his release Mr Sheehan said: "I am totally innocent. The whole reason for my arrest is an attack on Sinn Féin and the party. The fact of bringing me in is an attempt to damage Martin. I have nothing to do with vigilantism, or I don't condone it," he said.
A group calling itself "Concerned Parents Against Drugs" had claimed responsibility for the abduction on December 7th. During the incident the abducted man's six-year-old daughter was left on the road in Castleisland at around 6 p.m. when four masked men bundled her father into the back of his own car and drove him to a remote area in Lyracrumpane, before burning the car and beating him.
Mr Ferris and Mr Gerry Savage, Mr Sheehan's father-in-law, were outside the Killarney Garda station on Mr Sheehan's release last night.
Sinn Féin members have complained of "constant monitoring" by gardaí in Tralee.
A father of four, Mr Sheehan said he had been arrested by gardaí while dropping his 16-year-old daughter to the school bus in Ardfert village.
Mr Ferris said he had met Department of Justice officials in Dublin in recent weeks about Garda surveillance and "harassment" of himself and Mr Sheehan.
"They are outside James's house evey morning in the last two months. They are watching me morning and evening," Mr Ferris said.
A senior garda in Tralee last night "utterly denied" a watch on the Sinn Féin members. He added: "We have a duty to protect life and property and to investigate all crime."
It was not Mr Sheehan's first time being questioned by gardaí, he admitted in Killarney.
"He has been a close friend of mine for a long time and has suffered the consequences," Mr Ferris said.
Confirming the release last night, a spokesman for the Garda Press Office said the matter would be placed in the hands of the DPP. The gardaí would "not dignify" the allegations of political motives with a comment.
A Government spokesman said it had no involvement in the arrest.