Borealis had initially been due to sail on 23 April. Instead, it will sail a now seven-night Sailing Around Iconic Ireland cruise, departing Liverpool on 22 May.
It will still be the first of Fred Olsen’s four ships to return to service once, though, cruising in UK waters can resume.
The line said the move came in response to the latest coronavirus lockdown in the UK.
Fred Olsen managing director Peter Deer said: “When we announced our new ’back in service’ plans in December, we had every confidence in these new dates based on the information available to us at the time.
“Since then, we have seen a third national lockdown imposed, and this must be taken into consideration for our plans in returning to service."
Deer said deferring Borealis’ return would give the line more time to consider and understand the developments around Covid-19, including the vaccine rollout and how this will affect operations.
“We were also conscious that guests on sailings in April and early May would be due to pay their final balances soon, which is why we have taken this decision now," said Deer.
“We are really looking forward to welcoming our guests back on board with us in 2021, and I would like to stress that we will not do so until we are confident that the time is right.”
Bolette will be the second Fred Olsen ship to return to service, currently scheduled to depart Dover on 29 May, followed by Balmoral, which will sail from Rosyth on 9 June.
Braemar will remain in lay-up until 2022.
All guests booked on cancelled sailings will be notified of the changes, and will be provided with a number of options including a no-quibble refund as part of Fred Olsen’s plain sailing guarantee.
