Disability charities have renewed their criticism of fitness-to-work tests after the government said almost a million people who applied for sickness benefit have instead been found fit for work.

The applicants were denied benefits after undergoing a work capability assessment carried out by private firms contracted to the Department for Work and Pensions (DWP). But disability charities said the tests were unfair and the system was failing to give people the support they needed to get a job.

The testers assessed 32% of new claimants for employment and support allowance (ESA) as fit to work and capable of employment between October 2008 and March 2013 – totalling 980,400 people, according to the figures published by the DWP on Saturday.

More than a million others withdrew their claims before reaching a face-to-face assessment, because they had recovered and either returned to work or claimed a benefit more appropriate to their situation.

Under the old system, 2.6 million people were on incapacity benefit when ESA was introduced in 2008.

In August 2010, 900,000 people had been claiming the sickness benefit for more than a decade.

The minister of state for disabled people, Mike Penning, said: "With the right support, many people with an illness, health condition or disability can still fulfil their aspiration to get or stay in work, allowing them to provide for themselves and their family."

The employment rate for disabled people has increased gradually over the years to 45%, a DWP spokesman said.

ESA is an income replacement benefit provided to people of working age who are too ill to work because of a health condition or disability.

There were 2.49 million people on ESA and incapacity benefit as of May 2013. ESA replaced incapacity benefit, income support and severe disablement allowance for new claimants from October 2008.

Philip Connolly, the policy manager for Disability Rights UK, said: "They are finding people fit for work when they aren't and they are not even giving them the support they need to get a job. It is a disgrace.

"People should go online and read the test, and judge for themselves whether the test is fair. They will almost always come to the conclusion that it is not."

Richard Hawkes, the chief executive of the disability charity Scope, said the work capability assessment should be more than an exercise in getting people off benefits.

He said: "The fit-for-work results are only half the story. We should be talking about getting a million more disabled people into work.

"Disabled people are pushing hard to find jobs and get on in the workplace. Nine in 10 disabled people work or have worked. Yet only about 50% of disabled people have a job right now.

"They face massive challenges when it comes to finding and staying in work. We need to make sure that as the economy picks up disabled people are not left behind. We've got to start by supporting more disabled people to find and stay in work."