The Home Office is planning to use disused cruise ships to house asylum seekers amid growing anger from Conservative backbenchers over the use of hotels in their constituencies. Ministers are looking at possible vessels including a former cruise ship from Indonesia, which would be moored in south-west England, the Guardian understands. During the Conservative leadership campaign last summer, Rishi Sunak proposed putting illegal immigrants on cruise ships moored around the country but was warned it could be illegal under the Human Rights Act and the European convention on human rights. Downing Street confirmed he had dropped the idea to use the ships to house asylum seekers, which critics said would amount to arbitrary detention, once he became prime minister last October. Sources suggested, however, that the cruise ships could be registered as hotels rather than detention centres to get around possible legal challenges. The immigration minister, Robert Jenrick, is due to make an announcement on Wednesday regarding asylum accommodation amid speculation that it will include the use of boats and military barracks. It could also disclose plans to make use of a clause in the levelling up bill to force councils to accept large-scale accommodation for those seeking asylum. Multiple reports on Tuesday night suggested a plan to house asylum seekers on giant barges normally used for offshore construction projects could also be announced. The barges are built to house hundreds of people, although a government source told the Times that plans were at an “early stage” and had significant practical issues that needed to be addressed. The disclosure comes as the Home Office admitted nearly 400 hotels across the country were being used to accommodate more than 51,000 people at a reported cost of more than £6m a day. Sunak is under pressure to come up with alternatives as Conservative MPs, including members of his own cabinet, object to plans to move some people from hotels into former military bases. Suella Braverman, the home secretary, is expected to announce alternatives to hotel accommodation as soon as this week. They are expected to be used for new arrivals initially, rather than to rehouse people who are in hotels. The prime minister managed to face down a potentially big rebellion on Monday as up to 60 Tory MPs attempted to amend the new illegal migration bill by giving UK courts the power to ignore rulings by Strasbourg judges. Whitehall sources confirmed that the government had “in recent months” examined plans including using cruise ships from across the world, which could be brought to the UK and then used to house asylum seekers. The ships would be moored off the coast, emulating an approach by the Scottish government, which housed Ukrainian refugees in two 700-cabin ships. They were docked in Glasgow and Edinburgh and could hold 1,750 people each. Braverman said she would not rule out the use of former cruise ships when questioned in December by a House of Lords committee. “We will bring forward a range of alternative sites, they will include disused holiday parks, former student halls – I should say we are looking at those sites – I wouldn’t say anything is confirmed yet. “But we need to bring forward thousands of places, and when you talk about vessels all I can say is – because we are in discussion with a wide variety of providers – that everything is still on the table and nothing is excluded,” she said. It comes amid a Tory backlash over hotels in constituencies being used to house asylum seekers. Ministers had also drawn up plans to use two military bases that were identified to house asylum seekers earlier this year – RAF Scampton, the Dambusters’ base in Lincolnshire, and MDP Wethersfield in Braintree, Essex. But they are facing opposition from local Conservative politicians. Council leaders in Braintree are taking legal action to stop up to 5,000 people being moved to the site over the space of a year. James Cleverly, the foreign secretary, who is the local MP, wrote on his Facebook page that Wethersfield was inappropriate as an asylum camp because of “the remote nature of the site, limited transport infrastructure and narrow road network”. The local council in Scampton is seeking listed status for the Lincolnshire base, while historians and RAF veterans have written to the government asking for the plans to be halted. One government source, asked about the possible use of cruise ships, said ministers were working to end the use of hotels and bring forward a range of alternative sites for longer-term accommodation. But they would not discuss details of individual sites or proposals that could be used for bridging or asylum accommodation. A government spokesperson said: “We have always been upfront about the unprecedented pressure being placed on our asylum system, brought about by a significant increase in dangerous and illegal journeys into the country. “We continue to work across government and with local authorities to identify a range of accommodation options. The government remains committed to engaging with local authorities and key stakeholders as part of this process.”