Some benefit claimants will be given pre-paid cards instead of cash, so they don't waste their money on alcohol, drugs and cigarettes, Iain Duncan Smith has announced.

The Work and Pensions Secretary set out plans to pilot the scheme, and said he had long believed that where parents fall into damaging spirals, such as drink or drug addictions or even large amounts of debt, there had to be ways to protect their children.

The scheme will test the use of prepaid cards, onto which benefits will be paid, and can only be used in certain shops and on certain goods.

Mr Duncan Smith said the system would help lift families "on the margins" out of poverty.

In his speech to conference, the former Tory leader also announced plans to roll out his troubled flagship Universal Credit welfare scheme nationwide from next year. The reform brings together six different benefits and tax credits into a single payment and is currently operating in the North West of England.

It is designed to ensure that benefits do not tail off too sharply if the unemployed do small amounts of work.