Ferry operator Caledonian MacBrayne has now turned away more than 270 passengers trying to break lockdown to reach west coast islands.
The total has almost doubled over the past two weeks.
The revelation comes as CalMac announced that it is to further extend its essential travel only timetable until “at least” the end of the month.
No future bookings will be taken until after June 30 as the company continues to work with the Scottish Government and Transport Scotland to implement future travel and transport guidelines.
But it also revealed that so far it has turned away 273 people since the introduction of essential travel.
It follows a crackdown on second home owners and day trippers, particularly on the Clyde routes.
The islands have had few cases of coronavirus.
The Outer Hebrides have had just six – the lowest in the country – with no confirmed cases since April 10 and no deaths.
But with a largely elderly population, the islands are especially vulnerable to an outbreak.
Managing director Robbie Drummond said: “We will continue to take our lead from the Scottish Government and Transport Scotland, while working closely with the communities we serve.”
The company said it will be continuing its checks on people travelling for non-essential reasons with port and ferry staff asking for proof that they are an island resident, or evidence that they are a key worker, before being allowed to board.
Passenger and vehicle numbers are down 95% across CalMac’s 28 routes as the majority of people have respected the advice to stay away for now.