The government has confirmed it has continued to use P&O Ferries despite condemning the firm over the law-breaking sacking of nearly 800 staff without notice.
It comes after the government terminated its “one-of-a-kind” agreement with the operator in response to the firm’s “unacceptable” treatment of its former employees.
It followed a review by the Department for Transport into government contracts with the operator in the wake of the mass sackings.
The Ministry of Defence (MoD) has since confirmed it used P&O for an army exercise taking place in Germany after the RMT transport union said it saw evidence the MoD had occupied slots on the operator’s Dover-Calais service.
Previously, the same exercise was completed using military air transport, but due to the ongoing support to Ukraine, the MoD said that was not possible.
The department also said that it was the first part of the exercise which required the use of ferries.
A government spokesperson said: “We do not have any contracts with P&O. The Ministry of Defence occasionally require specific logistics operations to support national and international security arrangements.
“P&O Ferries are the provider of last resort in such situations, on an exceptional basis only.”
RMT general secretary Mick Lynch slammed the MoD’s use of the P&O services as a “new low, even by this zombie government’s sinkhole standards”.
Mr Lynch also called on the government to issue a statement barring public contracts with P&O Ferries and its parent company DP World.
P&O was widely condemned after it replaced 786 crew members with cheaper agency workers on 17 March.
Politicians and trade unions said the decision put the safety of ships at risk.