Emails sent by the public to an Office of Fair Trading (OFT) inquiry into Isle of Wight ferry services were "accidentally deleted", the OFT said.
It carried out a competition study into the services following a complaint signed by 8,000 people.
It said 10 to 15 emails, submitted between 17 February and 10 March, had been read but were later deleted.
Following the study, the OFT concluded that the matter should not be referred to the Competition Commission.
It has instead begun a consultation on its findings, which members of the public can comment on until 12 August.
Red Funnel and Wightlink offer vehicle and passenger ferry services to and from the Isle of Wight, while Hovertravel provides a passenger-only service.
People had complained about high prices, unclear charging and declining service.
Isle of Wight ferry services
Car ferry service: East Cowes to Southampton
Passenger fastcat: West Cowes to Southampton
Car ferry service: Fishbourne to Portsmouth
Car ferry service: Yarmouth and Lymington, Hampshire
Passenger fastcat: Ryde to Portsmouth
Passenger service: Ryde to Southsea in Portsmouth
The OFT admitted deleting some emails during the first few weeks of its inquiry, and said it had asked members of the public on its website to resubmit their comments.
The findings of the OFT study, which were published on Friday, found the ferry services were frequent, comprehensive and generally reliable.
It said many of the complaints about pricing "came from island residents who wanted to take a car across the Solent".
The OFT added that there were barriers for new competitors, such as limited room on the island for berthing facilities, but these were not caused by the ferry operators.
Isle of Wight MP Andrew Turner, who led the campaign for an inquiry into the ferry companies, said he was "not giving up on trying to secure a full investigation".