George Osborne's pledge to cut an additional £12bn from the benefits bill, repeated at the recent budget, has always been strangely thin on detail.

The Conservatives make much of the fact that they are specifying the cuts they plan to make, unlike rival parties. But David Cameron, like his Chancellor, was unwilling to clarify further in this week's live TV appearance.

The strongest argument he offered was that as the coalition has already cut £20bn from benefits, it will be able to find another £12bn. But this is bogus logic. It is sensible to assume that the most easily realisable savings have already been achieved. If they have been achieved without pain that is no guarantee that further cuts can also be painlessly realised.

But of course the cuts have not been painless in any case. The DWP has investigated 49 suicides of people claiming benefit since 2012, and has made recommendations for change in relation to 33 of them, but will not reveal what they are or why.

The bedroom tax caused anguish until a new fund was brought in to mitigate its impact. A doubling of sanctions has driven many claimants to food banks. And the Scottish Parliament's welfare reform committee has found that the cuts have disproportionately affected disabled people and families with children.

So it is reasonable to ask where the next savings will come from. It is widely accepted that existing proposals only account for around £2bn of the £12bn target. Leaked documents from the DWP include a number of suggestions, including the taxing of disability benefits and reductions in Employment and Support Allowance (ESA) for people deemed unfit to work. However the department says this was speculative work, not policy.

Other analyses suggest working age claimants of these and other benefits could lose an average £19 a week. Those claiming housing benefit and disability benefits would lose out as well as those on ESA.

For those on standard ESA of around £100 a week, a £19 reduction is brutal.

The calculation comes from an independent website, but academics fear they make sense. The IFS says also says the Tories' £10bn gap can only be filled by including 'less palatable' options involving 'overnight takeaways' from certain families.

We need to consider who cuts target. Benefit cuts are often popular with many voters, but despite much mythologising, most claimants are not exploiting the system. Those claiming ESA, for instance, are exposed to a medical testing scheme of remarkable rigour.

Those deemed unable to work are predominantly those with serious disabilities, those who have suffered a serious medical crisis, or have chronic medical conditions.

Cutting child benefit so that it is only paid for the first two children, as the leaked documents propose, delivers very limited savings, but effectively punishes every child in a large family.

Are these cuts we wish to see? The kind of cuts which are being envisaged would have much wider ramifications for society at large, rather than merely the recipients of benefits.

Mr Cameron and Mr Osborne should end the speculation by explaining their true plans.