A disabled man starved to death four months after his benefits were cut, an inquest has heard.

Mark Wood, 44, weighed just 5st 8lbs when he was found dead in August.

He had been told in April that he was fit to work, despite having been diagnosed with Asperger syndrome, obsessive compulsive disorder and a range of phobias, including a phobia of certain foods.

His housing benefit and employment support were taken away, leaving him just £40 a week disability living allowance to cover all of his costs.

Coroner Darren Salter ruled that his death was probably "caused or contributed to by Wood being markedly underweight and malnourished". His doctor, Nicholas Ward, testified that given Wood's body mass index, it was not possible for him to survive.

Wood had been unwilling to ask his family for help, and was not aware that his benefits had been cut, his relatives said.

Dr Ward told the inquest at Oxford Coroner's Court that he had not been consulted by either the company, Atos healthcare, that carries out health assessments for those on benefits, or the Department for Work and Pensions before the decision to remove Wood's benefits was made.

He said he had given Wood a letter before his death to pass on to the Jobcentre, in which he expressed concern about his patient's psychological ability to deal with their decision, and re-stated his belief that Wood was not well enough to work. He said he did not know if Wood had managed to deliver it.

"He was an extremely fragile individual who was coping with life," said Ward.

"Something pushed him or affected him in the time before he died and the only thing I can put my finger on is the pressure he felt when his benefits were removed."

Mark's sister Cathie Wood, 48, of North Oxford, described her brother as a "sweet and gentle" person.

"When the police found him, there was very little food in the house, just half a banana and a tin of tuna," she told the Mirror.

She said that her brother had only been interviewed for half an hour before the decision to cut his benefits was made, and called for the government to provide the disabled with independent advocates to help them make their case to assessors.

"I would like Iain Duncan Smith to stop talking about this as a moral crusade, and admit that this whole process of reassessing people for their benefits is a cost-cutting measure. I want David Cameron to acknowledge the personal costs of this flawed system. This is not just someone being inconvenienced – this is a death," she said.

A spokesman for Atos Healthcare said: "We carry out assessments as professionally and compassionately as possible."

A DWP spokesman added: "A decision on whether someone is well enough to work is taken only after thorough assessment."

Tom Pollard, Policy and Campaigns Manager at Mind, said: "We were deeply saddened to hear of the death of Mark Wood.

"Unfortunately this tragic case is not an isolated incident. We hear too often how changes to benefits are negatively impacting vulnerable individuals, who struggle to navigate a complex and increasingly punitive system.

"We know the assessment process for those applying for Employment and Support Allowance is very stressful, and too crude to accurately assess the impact a mental health problem has on someone's ability to work.

"This leads to people not getting the right support and being put under excessive pressure which can make their health worse and push them further from the workplace.

"We urgently need to see a complete overhaul of the system, to ensure nobody else falls through the cracks."