The electoral commission has backflipped on its ruling that Advance Australia election ads targeting ACT Senator David Pocock breached electoral laws.
The conservative lobby group Advance Australia campaigned against independent ACT Senator Pocock before the federal election via pre-recorded phone calls.
The Australian Electoral Commission previously ruled the phone-based ads targeting Mr Pocock were misleading and deceptive.
However, the commission has said a further investigation determined the calls were not robocalls.
"Following an investigation, the AEC determined that Advance Australia's calls were not robocalls and as such did not breach the authorisation requirements of the Commonwealth Electoral Act," a spokesperson said.
"The AEC's comments before the federal election were provided on the understanding that the calls in question may have been automated public robocalls that needed to comply with the authorisation requirements.
"Subsequent investigation confirmed that this was not the case."
Senator Pocock said he was "perplexed and disappointed" by the decision, and wants more information on the investigation.
He said he had written to the commission asking if they would prosecute Advance Australia over the calls, and corflutes which depicted him as a secret Greens member.
"I am perplexed and disappointed by the AEC's statement regarding Advance Australia's robocalls," the senator said.
"My campaign was contacted by dozens of people across the community who had received calls from Advance Australia on the eve of the election spreading misinformation about me.
"I would welcome further information from the AEC relating to their investigation and how they have reached this conclusion."
Signs which depicted Senator Pocock and Warringah independent MP Zali Steggall as wearing Greens t-shirts were determined to have breached electoral rules.
An Advance Australia phone-based survey on the eve of the election also targeted The Canberra Times, accusing the masthead of bias.
Former ACT senator Zed Seselja - who was ousted from his spot by Senator Pocock - has denied any links to Advance Australia, which targeted independents and left-wing parties at the last election.
Mr Seselja's former advisor Liz Storer, his former staff member and relative Steve Doyle and former chief-of-staff David Hutt have all been employed or contracted by the group.
Advance Australia did not respond to a request for comment.