The deputy prime minister has been accused of making “disgraceful” comments after claiming that the firefighters’ union had raised safety concerns over a barge due to house asylum seekers because of close links to Labour. Oliver Dowden suggested that the Fire Brigades Union’s affiliation and donations to the opposition were a motivating factor behind fire and overcrowding concerns raised about the Bibby Stockholm in Portland, Dorset. In reply, the FBU’s assistant general secretary, Ben Selby, called for a serious approach to overcrowding concerns on the vessel. “Fire safety is a serious matter and this situation calls for a grown up approach. We are sounding the alarm because it is our duty to do so. “Speaking out for the safety of the public and our members has nothing to do with our democratically decided political affiliation, and it is disgraceful for Oliver Dowden to suggest this. “As Mr Dowden knows, we have invited the home secretary to meet with us to discuss the significant concerns we have in relation to fire and operational safety onboard the Bibby Stockholm and in other asylum seeker accommodation. We have yet to receive a response to our request.” Dowden was asked on Thursday to explain why there had been delays in placing asylum seekers on the vessel. Ministers have claimed that it is a key part of the government’s strategy to deter people from arriving on UK’s shores in small boats, and would help cut the £6m-a-day cost of housing asylum seekers in hotels while their claims are processed. But last-minute interventions by the Health and Safety Executive have caused delays and increased claims that the vessel is not fit for purpose. Asked on BBC Radio 4’s Today programme about the FBU’s comments to the Guardian that the barge could be a floating “death trap” for asylum seekers, Dowden said: “Of course, we’ll take into account those concerns and that’s exactly what we’re doing. “I would just gently say the Fire Brigades Union has donated £850,000 to the Labour party since 2010. It is affiliated to the Labour party, and I’m afraid what we see with this is exactly what we saw with trying to pass the legislation earlier this year through parliament.” After a series of delays, government sources had suggested the first arrivals would come next week but Dowden hinted at another possible delay. “We have to undertake a number of inspections and other measures to make sure that these vessels, and this vessel in particular, is suitable and ready. “We are confident that we will be able to address all of these concerns, I’m absolutely certain of that, and I’m absolutely certain we will be able to get people on this vessel in the coming weeks.” The union has called for an urgent meeting with the home secretary, Suella Braverman, to discuss fears about overcrowding and access to fire exits on the barge. Sources confirmed reports that fire safety concerns did lead to initial setbacks, saying a door had been put on the wrong way around. There is another hold up because the Health and Safety Executive is looking at working practices for port authority workers, the source said. Shelter, the homelessness charity, has sent questions to the government about safety and wellbeing on the barge. Rose Arnall, a solicitor at Shelter, said: “We have read some concerning reports about the vessel and ones like it. So, the purpose of our letter is to seek information and clarity from the Home Office that the safety and wellbeing of those onboard, including their ability to access essential information, health and social services, has been properly considered and prioritised.”