The ferry ran aground on June 21 with 47 people aboard - prompting inquiries from the transport agency, Maritime New Zealand and the Transport Accident Investigation Commission.
A leaked Interislander safety bulletin said a crew member accidentally executed a course change through the ship's auto pilot system soon after it left its Picton berth.
The crew then struggled for nearly a minute to regain control of the boat, but by then it was too late to stop the ferry crashing into the shore of Titoki Bay.
Earlier this week, New Zealand First tweeted a theory that a crew member left the boat on autopilot while they went for a cup of coffee.
"We don't need a month-long enquiry or three or four months while they try and do PR and damage control and cover their butts. Tell us the truth right here right now," Peters said.
When asked if he thought KiwiRail was covering up the real cause of the accident, Peters replied "I don't think it, I know it".
But Interislander operations general manager Duncan Roy rejected the suggestion.
He told RNZ the leaked document indicated the agency knew what had happened but it was up to the investigating bodies to determine the "how and why".
"I can state there's no cover-up. We're engaging in the proper process and with a concentration on getting the facts and being fair and reasonable to our people as we go through this investigation," Roy said.
Labour Party transport spokesperson Tangi Utikere said Peters' "delving" into the causes of the accident was extremely unhelpful.
He said the nation expected the investigations to be completed in a timely manner, but it was just as important their integrity was not compromised by political interference.
"What we did hear recently from KiwiRail is them going out saying that no one was on a coffee break as such. My read of that is they were forced to do that to quell some of the concerns that Winston Peters or the New Zealand First Party had put out into the public realm," Utikere said.
The Interislander safety bulletin showed a crew member prematurely selected a turn that should have taken the boat about a shore point called The Snout.
The error sent the boat directly into Titoki Bay - nearly a whole nautical mile ahead of The Snout.
John Riding has worked as a Maritime Consultant for nearly 30 years.
He said one of the lessons learned when the Aratere nearly ran aground in 2006 was that the ferries should always be under manual control while travelling through the Marlborough Sounds.
"To be on autopilot at Mabel Island is crazy and I can't believe for one second that's what Interislander's procedures say," Riding said.
"It shouldn't be happening, because Mabel Island is still a hazard, but after that the next hazard - only just around the corner - is at The Snout."
Maritime NZ lifted its detention notice on the Aratere yesterday.
Just before 2pm today the ferry limped into Wellington harbour escorted by a tug boat and under the watchful eye of harbourmaster Grant Nalder.
"Maritime New Zealand have put conditions on it and so have the harbourmasters at either end," Nalder said.
"So you'll also see one of the Wellington tugs is just accompanying the vessel from when it gets into the channel, until it gets up to the berth."
KiwiRail is yet to confirm when the findings of the investigations into the accident will be released.
