The three new larger Wightlink ferries replace the old fleet
Controversial new larger ferries have entered service between Hampshire and the Isle of Wight.
Wightlink is introducing three new ships on its Lymington to Yarmouth route as part of a £57m investment on its services to the island.
But the new larger vessels have attracted opposition amid claims they create greater wash, potentially damaging the Lymington River.
Wightlink said it has complied fully with legal environmental obligations.
But Wightlink have been accused of bringing in the ferries before environmental concerns have been resolved.
A strongly-worded statement issued by Peter Griffiths, the chairman of the river's management trust the Lymington Harbour Commissioners (LHC), said: "Wightlink have defied the will of all the regulators in deciding to introduce their new ferries before the necessary safety trials are complete and the environmental concerns have been resolved.
"They have taken this action despite repeated requests from the LHC and their previous undertaking not to do so.
"They claim that they are justified because of the needs of the Isle of Wight, but the real problem that has lead to this situation is Wightlink's determination to design and build ferries in advance of meaningful consultations with all the regulators.
"As a result, all subsequent consultations have taken place against the commercial necessity on the part of Wightlink to introduce ferries that had already been paid for.
"We have once again requested Wightlink to desist from this action, and are contacting all the relevant government departments for support in preventing it.
"However, if Wightlink go ahead without completion and acceptance of the risk assessment we will be providing whatever harbour patrols are appropriate to help safeguard other river users."
The ferries were built in Croatia as part of a £57m investment
The W class ferries were due to enter service last September. They were built in Croatia exclusively for the route and will replace the existing 35-year-old fleet.
LHC does not have the power to prevent the new ferries sailing.
But in a report Natural England concluded: "The introduction of the W class ferries can be expected to prolong ferry-induced impacts on inter-tidal habitats and consequently further losses are likely to be attributable to ferry operations, even when mitigated by recent reductions in speed."
In a statement on Tuesday on its website, Wightlink said its environmental consultants, ABPmer, disagreed with Natural England's conclusions.
It added: "On the basis of clear advice from ABPmer, Wightlink is confident that the new ferries will not have an adverse effect on the integrity of the mud and salt marshes in the Lymington estuary."