The SNP have accused Conservative ministers of introducing targets for benefits sanctions by the back door.

Anne McLaughlin, the Glasgow North East MP, said that one of her constituents, who works for the Department of Work and Pensions, had been given an "aspiration" for the number that they should impose.

The party has called for a widescale review of the sanctions regime, including the criteria used.

But David Cameron defended the sanctions system saying that it was being "fairly applied".

Ms McLaughlin said: "There have long been allegations of DWP staff being under pressure to hit targets for the number of benefit sanctions they slap on the vulnerable.

“But it doesn't matter what you call them - targets fail to take account of the devastating impact the withdrawal of vital welfare payments has to an individual.

"Benefit sanctions also do nothing to support people into work.”

She added: "I think the Prime Minister should have some aspirations himself and aspire to actually help people on low incomes instead of unfairly targeting them as part of the Tories' all-out assault on the poor."

Challenged on the issue at Prime Minister's Questions, Mr Cameron defended the current regime.

He told Ms McLaughlin: "Sanctions in a benefits system are important.

"We want a benefits system that is there for people who cannot find a job and need support, but it not should not be a lifestyle choice and if people can work, they should work.

"That is why we have a sanctions system, and I believe that the sanctions system is fairly applied."