Confusion over tax credit repayments will put low-income families at risk of further hardship, the Child Poverty Action Group has warned.

The complexity of the tax credit system could make it difficult to establish whether families have been overpaid due to the government's error or their own, CPAG's head of policy, Paul Dornan, said.

The government has announced that overpayments will be written off if tax officials made the error.

The decision follows two critical reports from parliamentary ombudsman Ann Abraham and the Citizens Advice Bureaux, which said the £1.9bn in overpayments were the result of system failure which had left many families destitute.

Backing the CAB's claim to write off payments except in cases of proven fraud, Dornan said: "It's not necessarily easy to prove official error. It is difficult to work out what is official error and what is individual error because of the level of complexity of the system."

He said the government had failed to make clear the importance of recipients reporting a change in their circumstances.

In a House of Commons statement last week, paymaster general Dawn Primarolo admitted many of the errors had been due to faults in the IT system.