LONDON — Prime Minister David Cameron says he wants to end Britain’s “sick-note culture” of fraudulent disability claims. But his new get-tough policy has left his coalition government in conflict with thousands of ill and disabled Britons.

In 2010, Dani Neumann, 28, was working as an administrator at Madame Tussauds wax museum and performing in musical theater when she was hit by a car while crossing the street. Left in crippling pain with severe nerve damage, she went in an instant from complete self-sufficiency to total financial dependence.

At every step of the way, she has had to fight hard for help. While the government pays her rent, it rejected her application for a welfare benefit that helps defray added costs associated with disability. It has postponed — since last May — scheduling an assessment for another benefit for unemployed disabled people.

Her only income now is $108 a week in temporary assistance.

“Because they’re trying to save money, they deny everything on application,” Ms. Neumann said in an interview. “If it hadn’t been for my synagogue’s help for the first five months after the accident, I would have been homeless.”

Perhaps one-third of the working-age population here receives some form of state benefit from Britain’s generous welfare system. Next to housing help, disability benefits are its highest welfare expense. The government spends $19 billion a year on one benefit, the disability living allowance, alone.

Populist newspapers like The Daily Mail have joined the government in highlighting how “benefit cheats” bilk the government by, for example, playing golf while on disability. Indeed, about 900,000 people have been claiming incapacity for a soon-to-be-defunct benefit meant to help sick or disabled people who are out of work, for more than a decade, the government says.

But advocates argue — and the government does not dispute — that many of the most entrenched recipients, like those who went on disability after being laid off from jobs in coal mines during the Thatcher years, have aged out of the system. The fraud rate, they say, stands at less than 1 percent.

“There’s been a media war waged against them — they’re being branded ‘benefit-scrounging scum,’ ” said Debbie Young-Somers, a rabbi at West London Synagogue, whose emergency hardship fund is helping pay basic expenses for Ms. Neumann and others.

A bill passed recently will make it harder to get and keep disability benefits. The government says the measure will not only save billions but also discourage long-term dependency.

“People don’t understand what these benefits are for,” said a spokeswoman for the Department for Work and Pensions, which administers them. Many who qualified under the old system might find they do not under the overhauled one, she said, asking that her name not be used in accordance with government policy.

“If you lose a limb, then whilst you’re getting used to becoming mobile you would be eligible for disability living allowance to help you with your mobility needs,” she said, referring to extra help for costs associated with disability.

“But there are people who get prosthetic limbs who can walk across the desert,” she added. “They do not have the same mobility needs as they did when they were first injured.”

The law tightens the criteria for the allowance, which goes to three million people. Already, thousands of applicants, including Ms. Neumann, say that they have been rejected, with little explanation.

One of the most contentious elements of the law limits support for unemployed disabled people.

Recipients of what is called the employment support allowance — except for the profoundly disabled or those believed to have less than six months to live — will be given job training and expected to rejoin the work force, even if their conditions preclude them from returning to their old professions. The money will stop after a year, except for those in the lowest-income brackets.

Advocates say that would most likely push 280,000 people out of the system.

“This is an arbitrary time limit placed on the amount of time they can get the benefit, whether they’re still too sick to work or not,” said Tom Cottam, a policy analyst with Macmillan Cancer Support, a major British charity. “The government has been very explicit that the time limit is a cost-saving measure.”

The previous Labour government required most new disability applicants to undergo face-to-face medical assessments. Those who received benefits under the prior system are being reassessed. The program costs $160 million, and assesses about 11,000 people a week. The process is guided by a checklist that includes criteria like whether the applicant can walk a particular distance, make a meal without help or hold a conversation.

An independent consultant hired by the government found that the system was plagued with problems, and advocates for the disabled say that not only is it grossly insensitive, but it is also singularly bad at determining who is and is not able to work. In a number of high-profile cases, people who are profoundly physically or mentally disabled have been found fit to work; some have died while waiting to appeal.

More than a third of those who used to qualify are being rejected, the government says. “To have such a high percentage who are fit for work just emphasizes what a waste of human lives the current system has been,” Chris Grayling, the employment minister, said recently.

But advocates for the disabled say the figures illustrate instead how ineffective the assessments are. About 40 percent of those who appeal after being rejected have won. There is a roughly eight-month backlog of cases. The appeal system is costing the government $80 million.

Meanwhile, people like Ms. Neumann are depending on the kindness of others..

“They say people live on benefits because they don’t want to work, but the reality is that you don’t have enough money for heating, to eat properly, to use public transport,” she said, reflecting on her $108 a week. “I understand that we’re in a recession and we need to cut corners at every turn. But why do you turn around and pick on the most vulnerable people?”

A version of this article appeared in print on March 31, 2012, on page A4 of the New York edition with the headline: Disabled Britons Say Welfare System Changes Endanger Them

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