A tough message on welfare is one of the ways that both Labour and the Tories think they can win in 2015. Ed Miliband upset some on the left yesterday with his plans to freeze child benefit and dock jobseekers’ allowance from under-21s not in employment or training, while the Tories constantly trumpet the gains they’ve already seen in people coming off benefits as a sign that their reforms are working.

But the suggestion today, in a leak to the BBC, that the Employment and Support Allowance is getting so expensive that the government could break its shiny new welfare cap, threatens to undermine the Conservative narrative on welfare. Iain Duncan Smith is rolling out universal credit to more claimants today, but the ESA leak will inevitably put his department back on the defensive as it faces allegations that it is out of control.

How Labour plays this will be interesting. ESA is paid to very vulnerable claimants who are often out of work because of long-term illness or a disability, and who have had to endure the very messy work capability assessment set up by Labour and expanded by the coalition. It will not be easy for Labour to come up with suggestions about how to cut this benefit further without enraging its own side. Other benefits, such as housing benefit, are often softer targets for sound and fury about controlling a budget. Labour will want to pounce on the coalition not controlling welfare as well as it should – but how does it do it without suddenly seeming callous?

Tags: UK politics, welfare cap, welfare spending