Strike action in Calais which stopped two ferries being passed over to their Danish buyer cost more than £13 million in repairs and lost revenue.

Eurotunnel revealed the scale of the damage caused by industrial action of French ferry workers as it officially handed over its the Rodin and Berlioz to DFDS Seaways, which it formerly operated under the MyFerryLink brand.

The Channel Tunnel operator signed a contract to sell the ships in June but has been unable to provide them until now after they were occupied by protestors who objected to the sale and job losses.

The ships must undergo repairs, the scale of which have been unveiled after liquidators sought to settle debts owed to the SCOP SeaFrance, the workers cooperative which operated the MyFerryLink ships on behalf of Eurotunnel.

Eurotunnel said the SCOP owes the company €22.7 million (£16.7m), of which €4.8 million (£3.5m) are penalties for late hand-over of the ships.

The remaining €17.9 million (£13.1m) relates to loss of revenue and repairs to the ships.

The figures were released to negate claims by liquidators of SCOP that MyFerryLink owed the cooperative €3.5 million (£2.6m) under conditions of the sale of the ships, of which €600,000 (£440k) has been paid.

In July, Kent Business revealed French ferry workers were running amok on the vessels – drawing graffiti, deploying evacuation slides and reportedly drinking the bar dry.

Eurotunnel sold the ships after a ruling by the Competition and Markets Authority earlier this year which said its ownership of the vessels broke monopoly rules.

The company is waiting to find out if the regulator will amend its ruling to allow it to operate the Nord Pas de Calais ship on the Dover to Calais route, which would allow it to employ about 200 former SCOP workers.