Work and pensions secretary Alan Johnson has announced the resignation of Doug Smith as head of the Child Support Agency.

Reports suggest the CSA has reached breaking point, with only 43 per cent of cash for single parents and children being collected.

A year ago the government claimed the problems would be solved by a simpler maintenance calculation and a £456 million computer system.

The news of Smith's resignation as CSA chief was announced during evidence to the work and pensions committee on Wednesday.

Speaking in the Commons, Michael Howard described the CSA as "in crisis".

The Tory leader urged the prime minister to "get a grip" on the continuing difficulties.

Tony Blair admitted that the IT problems should be "sorted out" because they had caused many problems.

But he said that the government had introduced a new simplified system for assessing payments owed by absent parents.