Doctors are charging sick and disabled people up to £130 for medical evidence to appeal decisions about their fitness to work, The Independent has learnt.

NHS GPs are telling patients they will only provide the necessary details to challenge controversial Work Capability Assessments if they pay. Others are refusing to help at all.

Citizens Advice say in many areas GPs are helping with an appeal only if patients pay a fee of between £25 and £130. There are also reports from 15 of its centres that family surgeries are refusing to provide evidence at all.

GPs who refuse to help – or charge increasingly high fees – argue that writing up medical evidence takes up time when they could be helping patients.

But Gillian Guy, chief executive of Citizens Advice, said: “Charging sick and disabled people more than £100 for medical evidence beggars belief. This process is clearly failing.”

A lack of evidence from doctors will make it more difficult for people to navigate what experts say is an already “flawed” system. The Work Capability Assessment, which is currently conducted by the private company Atos Healthcare for the Department for Work and Pensions (DWP), has already been beset by criticism.

More than 600,000 of the 1.8 million assessments carried out by Atos since 2009 have been the subject of an appeal, at a cost of £60m. Around a third of the appeals succeeded.

After an investigation by the DWP, which found that two in five of Atos’s written reports were not fit for purpose, the company will no longer have a monopoly to carry out the assessments.

The shadow Employment minister, Stephen Timms, said: “This is further evidence of the Government’s failure to manage the Work Capability Assessment, and it is disabled people who pay the price. The Government must urgently rebuild a system that is fit for purpose.”

In East Staffordshire, many patients are turned away by their GPs when they request support, while others are charged up to £130. Dawn Green head of East Staffordshire CAB, said: “We’ve noticed a massive increase in those asking for help. It seems almost everyone with mental illness gets no score.”

In Wigan, patients have been refused help, or, in some cases, charged up to £115. Four surgeries in Sunderland have refused to provide evidence, while in Wyre Forest, Worcestershire, patients are typically charged between £25 and £40. In Sydenham, south-east London, some surgeries have refused to provide evidence, while others charge up to £40 for letters only two or three lines long.

In north Devon, people can be charged between £50 and £100. In Knowsley, Merseyside, patients are refused help or charged between £45 and £75 for basic evidence. In Plymouth, GPs tell patients they cannot provide the service. Two surgeries in Islington, north London, have refused to provide evidence, while others have charged up to £70.

A spokeswoman for the British Medical Association said: “We have GPs across the country whose workload is ultimately increasing because of a fundamentally flawed work capability assessment.”

Atos said yesterday: “It is simply wrong to say that Atos are the reason for successful appeals. We are sorry when we do not meet our own high standards but can reassure that a ‘C’ grade report does not mean the assessment was wrong and there are checks and balances throughout the system so that the correct decision on benefit is made.”

A spokeswoman for the DWP said: “Since 2010 we have considerably improved the process, but anyone who disagrees with the outcome of their assessment can appeal, so it isn’t surprising that a number of people do.

Case study: Jim Grimwood was charged £40 for copies of his medical records

Jim Grimwood, 58, of Wearhead, Co Durham, had been a computer programmer for 20 years when he was forced to give up work because of his Parkinson’s disease.

I was diagnosed in 2005 but I put up with it for a long time before I had to finish work in 2011. When my medication is working, you can’t tell there’s anything wrong, but I get tired easily, I’m very stiff and I get a lot of muscle pain. The most visible symptom is a tremor in my right arm. When I’m like this I can’t use a keyboard.

The first Atos doctor I saw didn’t know anything about Parkinson’s – he didn’t even recognise the medication I was on. He scored me zero out of 15, with 15 being the most unable to work. They said I should be able to return to work within three months; I couldn’t believe it.

A year later they stopped my benefits and the benefits advice people said I should apply again. The hospital charged me £40 to provide my medical records. I had to pay that out of my pension. In the second assessment in January 2012, they granted me ESA but they said I could consider a return to work in 18 months.

My benefits will be stopped again in November, so I’ll have to go through the same thing again.