The second P&O ferry has passed its safety inspection, according to theMCA.
After being held for two weeks, the Pride of Kent can now join the Spirit of Britain.
P&O will be running a single ship schedule until 12 May.
The Pride of Kent can begin operations when P&O Ferries are ready, according to a spokesman for the MCA.
At the moment, no further inspections of P&O ferries are planned, but will be done at the request of the company.
The Pride of Canterbury and the Spirit of France are still out of service as P&O operates four ferries on the Dover to Calais route.
The European Causeway, which was cleared to sail by the MCA, was adrift for hours after losing power.
The company said it was a mechanical issue.
Grant Shapps, the Transport Secretary, has called for P&O to repay the money it received from the government during the coronaviruses.
Several demonstrations have been organised by the union in protest at the dismissal of the seafarers.
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