Many people with dementia in care homes go for hours without speaking a meaningful word to anyone, a report from the Alzheimer's Society suggests.
Interaction and stimulation are crucial, the charity says
A large number of relatives surveyed by the charity also said their loved one was rarely taken outside, while basic hygiene needs were not always met.
The Alzheimer's Society is calling for all care staff to receive mandatory training in dementia care.
The problem can only worsen, it warns, as more people develop the condition.
The Alzheimer's Society surveyed 3,500 people, including relatives of those with dementia, care home staff and managers.
Its research found some residents spent less than two minutes in every six hours talking to staff or other residents.
Interaction and stimulation are thought to help manage dementia, which affects two-thirds of care home inhabitants.
More than half of people with a relative in care said there was not enough for them to do each day, and one in four said they did not feel informed about the care and treatment of a loved one.
The society argues that, under the current system, poorly-paid 16 and 17-year-olds are being asked to enter homes with minimal experience and manage people "with very serious conditions".
"There needs to be a serious rise in expectations as to standards of care both relatives and residents can hope for," said Andrew Chidgey, head of policy and campaigns at the Alzheimer's Society.
While two thirds of care home residents have some form of dementia - some 244,000 people - only 60% of these are in special dementia-registered beds.
This situation is set to get worse amid forecasts that the number of people with dementia will grow by around 40% in the next 20 years, by which point around 1m people will be living with the condition.
The Alzheimer's Society says it wants a firm commitment from government that more money will be allocated to make training mandatory.
It says this could ultimately prove cost effective, arguing that many people with dementia are unnecessarily managed with medication, at an estimated cost of £80m each year.
Local authorities were key to driving up standards, the society said, as they were in the position to award contracts only to those care homes which met the necessary requirements.
But Frank Ursell, chief executive of the Registered Nursing Home Association, said local authorities were often not in the position to negotiate as bed numbers were so limited.
"We would heartily welcome more training, without a doubt. But moreover, we need more dementia beds - around 65% more than we have at the moment," he said.
"The government are not approaching dementia in any way that is realistic. Nothing is going to change until they change their attitude. If this report gets people thinking about this problem, that will be a very welcome start."
Health Minister Ivan Lewis said a "new strategy" will be published late next year which "will include a clear focus on improving the quality of care in nursing homes ensuring staff have the necessary expertise and sensitivity".
"Today, we are making a start by publishing a best practice guide to ensure clinicians and commissioners involve people with dementia and their carers in the development of new services."