Arguing that the UK should be a “lower tax, lower welfare society”, the prime minister said it was wrong to treat “the symptoms of the social and economic problems we face” while “ignoring the causes” of low pay.

Mr Cameron’s speech comes amid a debate over plans for £12 billion in welfare cuts, the details of which have not been revealed.

The UK government says the welfare bill has to take its fair share of cuts as part of its plan to balance the books and eliminate the £90bn deficit by 2017-8.

With ministers having pledged to protect pensioner benefits and child benefit, speculation mounts that much of the £12bn would come from tax credits and housing benefit.

Ahead of next month’s Budget, in which chancellor George Osborne is expected to give more details of which entitlements will be cut, Citizens Advice Scotland (CAS) has revealed its concerns over the damage of a likely cut to the £29bn annual tax credit bill.

CAS spokesman Rob Gowans said: “For the last few years the CAB service has seen first-hand the problems that the welfare reforms have caused for vulnerable people in Scotland, and we are concerned at the impact that further cuts will have.

“Following previous changes to the tax credits system in 2012, for example, we know that 97,300 fewer working families in Scotland have received tax credits. That’s a fall of 27 per cent. Over that same period, Scottish CABs saw a 12 per cent increase in the number of new cases related to tax credits.

“CAB advisers across Scotland are reporting a growing number of cases where people are in work, but are struggling to pay for essentials. Common problems include low pay, childcare costs and availability, misuse of zero hours contracts as well as lack of support from the in-work benefits system.

“We will continue to offer free, confidential advice to anyone who is struggling financially, but we will also be pressing ministers to spell out how people will be protected from the damaging impact of further cuts.”

@CitAdviceScot