It’s tempting to think that the sudden deterioration of my mother’s mental health could be linked to Brexit and our country’s collective nervous breakdown. I know it’s just a coincidence. But I believe that she and many others with Alzheimer’s disease are Brexit victims because the government’s focus on leaving the EU has created a policy vacuum that has cut adrift the most vulnerable people.

A few months after my mother went into a care home with dementia, my brother and I are once again navigating the care system on our own, after she was told that the home could no longer cope with her “challenging behaviour”. Mum, a retired cookery and needlework teacher, now aged 90, seemed to have settled until about three weeks ago, when she became paranoid and delusional. The staff told us of aggressive behaviour requiring more specialised dementia care, which they cannot provide.

Because Mum has the dubious privilege of having assets of more than £23,250, she is denied any financial help for her care needs. Like many other “self-funders”, we sold the family home in order to pay for her accommodation. Now, as we are hoping to move her into a dementia nursing home that has a specialised unit for challenging behaviour, there would be a big difference in fees. We’d been warned that the bar is “set very high” by the NHS before they would agree to full funding.

I can’t fault the care and compassion shown by the staff at Mum’s home, nor by the social workers

Theresa May has long promised a green paper on the future of social care. It is supposed to address the unfairness in a system in which people with a mental health condition such as Alzheimer’s disease, for which there is no cure, have to pay for their own treatment depending on their assets – unlike cancer patients, whose medical treatment is NHS funded. It is also expected to tackle how health could be better integrated with social care, which is currently funded by cash-strapped local authorities. The green paper was initially announced for June 2018. But the Department of Health and Social Care tells me no date has been fixed, although that it is intended to happen “at the earliest opportunity”. Could it be that the government is in no hurry, after Brexit, to pick up another politically sensitive reform?. This despite the open letter from leading health experts earlier this month warning that social care is “on the brink of collapse” and is a “national disgrace”.

Meanwhile, given the spectacular decline in Mum’s mental health, my brother and I have had to become familiar with a whole new lexicon during our urgent quest to find that elusive place – a care home in her local area with at least a “good” rating from the regulator, and an available bed. We put her on the waiting list of three homes, but kept on looking as her condition was worsening by the day. By this time she had been served with a deprivation of liberty safeguarding (DoLS) order, to protect her safety and that of others.We found her a pleasant room in a residential dementia home, which had locks on the doors unlike her present home. We’d been told by the district nurses that this was the category of home that Mum required. However, when the home manager visited to assess Mum, she was rejected because of her “challenging behaviour”. They saw her a few minutes after I’d found her clutching torn-up pages of her diary and refusing to let go, hissing: “That’s the evidence!” In recent days she’d been accusing people of stealing from her and was demanding that the police should be called. So our search continued until We found a place that provides dementia nursing with a separate wing for challenging behaviour. You can imagine what we saw and heard in that wing. It was heartbreaking.

I can’t fault the care and compassion shown by the staff at Mum’s home, nor by social workers. I’ve had phone calls out of the blue from social workers wanting to know how she’s doing. But moving Mum into the new care home is throwing up obstacles, including funding, which I understand should be covered because of her deepening mental health issues. “It’s a minefield,” one social worker said to me.

For us it’s a distressing situation, and it must be terrifying for Mum. However, there is the occasional crumb of comfort. When my brother and I visited the challenging-behaviour wing of the care home where Mum will hopefully be taken in, a staff member looked up after noting her name.

“One of my teachers was a Mrs Penketh,” she said. “I wonder if it’s the same person?” It turns out that Mum taught her how to darn socks in needlework.

“It would be ace if she comes here,” she said. I had to fight back my tears.

• Anne Penketh is a journalist and author