Pensioners and disabled people often face delays in receiving their benefits due to blunders by the government agency responsible, an influential committee of MPs has found.

In a report published on Tuesday, the Commons public accounts committee found that 40 per cent of appeals against benefit decisions are successful, a quarter of which are a result of errors by Benefit Agency staff.

And one in 10 appeals were won on grounds of the misinterpretation of medical evidence by agency staff.

Indicating significant problems in the administration of the benefits system, the MPs also found that £40 million is wasted annually by the Department for Work and Pensions which pays benefits to those who are not entitled to them.

The report found that up to 30,000 people face unnecessary medical checks when applying for incapacity and disability benefits.

MPs were also critical of the SEMA group, which performs 1.3 million assessments.

The committee discovered that SEMA regularly overbooked clients to ensure efficient work by doctors - around 17,000 patients are turned away because of this policy.

The report also concluded that one in 10 of these assessments were "sub-standard".

"The purpose of medical assessment is to ensure that only eligible claimants receive incapacity and disability benefits," said committee chairman and Conservative MP for Gainsborough Edward Leigh.

"But claimants have a right to expect prompt and accurate decisions, and an efficient and considerable handling of their claims by doctors undertaking medical assessments and providing medical information."

Patients turned away from appointments should be appropriately compensated, the report recommends, while the DfWP should set targets for the number of correct benefit decisions.

The process of decision making should also be speeded up, by allowing medical staff other than doctors to complete assessments.

Paula Twigg, of the Child Poverty Action Group, said: "The government should be deeply concerned that some of the most vulnerable people in society are not getting the financial support when they need it most. We call on the government to take note of this hard-hitting report and take action to ensure that those who need support get it when they need it."