Increasingly severe benefit sanctions must be reviewed amid little evidence the government understands the impact, a powerful cross-party committee of MPs has said.

The Public Accounts Committee, which probes government spending, said a new system of warnings rather than immediate sanctions should be tested.

The report concluded that the government is unable to estimate the impact sanctions are having on the public purse.

It also found a huge variation in the scale of sanctions imposed, with some job centres and Work Programme providers referring twice as many people for punishment as others.

Mark Harrison, chief executive of the charity Equal Lives, which helps people appeal sanctions, said: 'The indiscriminate and wide use of benefit sanctions against disabled people is just one of the reasons the UN found the UK Government guilty of grave and systematic violations of human rights. This is a cruel and unjust regime which treats benefit claimants more harshly than people convicted in the courts of crimes.'

Meg Hillier, the Labour MP who is chairman of the Public Accounts Committee, described sanctions as a 'blunt instrument'.

'It is an article of faith for the Department for Work and Pensions that sanctions encourage people into work. The reality is far more complex and the potential consequences severe. Sanctions and exemptions are being applied inconsistently, with little understanding of why.'

MPs also found some people who had been sanctioned stopped claiming without finding work, putting more pressure on other services.

'Suspending people's benefit payments can lead them into debt, rent arrears and homelessness, which can undermine their efforts to find work,' Ms Hillier added. She said a 'far more nuanced approach' to sanctioning claimants was needed. 'As a priority the Government must make better use of data and evidence from the frontline to improve its understanding of what best supports both claimants and the interests of taxpayers in general,' she added.