An absence of satisfactory answers in an official parliamentary report might be taken to be a flaw.

In fact, the gaps in the House of Commons' Work and Pensions Committee report on benefit sanctions are highly revealing.

When the money a person uses to survive is stopped, one would expect the rules around that to be clear and well defined. The committee says they are not.

One might expect the Department for Work and Pensions to publicise the findings of investigations it has made into 49 suicides of claimants and whether those claimants had been sanctioned. They do not.

You would expect the government to offer proof that stopping people's income is successful in encouraging them to find work. It doesn't exist, the committee says. One might think such evidence would be sought before quadrupling the minimum length of sanctions. The UK government did not.

Among many other such questions raised by the report, one might think such a sanctions policy - if not driven by ideological concerns - might focus on those most resistant to work and training. This is not done, and the report's call for a pilot scheme to test this approach seems eminently reasonable.

There is a lack of evidence to justify the use of sanctions, which has more than doubled under the present government. Yet evidence continues to pile up of the problems they cause - from Citizen's Advice, which finds itself having to help people who have no way to buy food, and who it says are often treated unfairly, from an alliance of churches which say families are being harmed by the policy, from academics and charities.

It is reasonable to conclude that this policy is driven by politics, not evidence. The scapegoating of claimants as the benefits bill is slashed may be seen as a vote-winner by political parties and both the Conservatives and Labour have endeavoured to appear tough on benefits.

But while it is right to ensure that the system is not exploited by those who have no intention of working, it is vital to remember that sanctions affect real people. As food banks multiply and are forced to move into ever bigger premises, the questions posed by critics of sanctions must be answered.

One of the biggest concerns is over hardship payments, which are available to those left without any source of money to buy food or fuel, but only after 15 days.

It is unacceptable on a human level to leave people, many of whom are already desperately poor, with nothing to live on. But it is also unacceptable to apply that policy in defiance of common sense.

It is hard to understand how sanctions can be helpful to any efforts to job search. Finding jobs requires bus fares, a topped up mobile phone, clothes. The social security system designed to protect people from disaster is now actively pushing some people into crisis.

The system must be reviewed, as the committee has urged again. Meanwhile any politicians arguing to extend or maintain the current, punitive system should be forced to produce the evidence to justify their position.