The transport secretary, Grant Shapps, has made an urgent intervention in the growing crisis over the welfare of 1,500 crew on five cruise liners, which British port authorities have detained after a raid on Friday. The Maritime and Coastguard Agency said it was detaining five of six ships it inspected on Friday morning over serious concerns about the welfare of the crew, some of whom have been stranded for three months in Essex. In a statement issued just before midnight, Shapps said the government would “not hesitate to continue to use every power within our control to safeguard the health and happiness” of the crew. The International Maritime Organization said it was on the verge of a humanitarian crisis. Some of the crew has been stuck on board for more than the legal limit of 11 months, unable to be repatriated to their home countries. The MCA sent investigators on board the six ships operated by British firm Cruise & Maritime Voyages following reports of hunger strikes, late payment of wages and one death. More than 150 Indian crew on one of the ships, the Astoria, have been stranded in Tilbury Docks in Essex for three months. They wrote to the Indian prime minister earlier this month to ask for help. One crew member died from “natural causes”, believed to have been a heart attack. Shapps said: “The welfare of seafarers is of the utmost importance and we take any reports of safety concerns around crew incredibly seriously.” The ships have been stranded since the start of the coronavirus outbreak, but most European crew members have been repatriated. It is believed there are also crew from Indonesia and Myanmar, some of whom will be flown home on Sunday. After its inspection the MCA said: “Surveyors found a number of expired and invalid seafarers employment agreements, late payment of wages and crews who had been on board for over 12 months. All these are in breach of the Maritime Labour Convention and the ships have been detained for that reason,” it said. The ships, including the Astoria which had been due to set sail for Portugal, will be detained until the breaches are resolved, said the agency. The remaining five ships are the Astor, the Columbus and Vasco de Gama, berthed at Tilbury and the Marco Polo in Bristol. The sixth ship, the Magellan, has not been detained because no significant deficiencies were found. The International Transport Workers Federation’s inspectorate co-ordinator, Steve Trowsdale, said that when the coronavirus outbreak hit the cruise industry the spotlight had been on repatriating passengers but not crews. “The cruise industry is in a real mess at the moment because of coronavirus. What we have is a situation where you might have had 4,000-5,000 passengers on board and the first priority has been to get them off and repatriated, but you will have had 2,000 -3,000 crew left behind and they have been largely ignored and don’t get the repatriation,” he said. Kate Ware, the director of safety and standards at the MCA and the UK’s permanent representative to the IMO, said the crew’s welfare “remains a top priority for us both as a flag and a port state”. The ships are all owned by Global Cruise Lines Limited and operated by the British firm CMV. The company said its crew had endured prolonged distress and that the issues of expired contracts and crew being onboard in excess of 12 months “occurred as a result of the enforced lockdown period and the Covid-19 travel restrictions for some countries”. Christian Verhounig, the chief executive, issued a public apology for the situation and said he hoped the sudden increase in support “raised awareness of the plight of our crew with the various embassies” and that they would assist CMV with the repatriation of crew members before the end of the month.