Campaigners say that without the increase the government will fail to meet its target to cut child poverty by a quarter by 2005.

The government target of halving child poverty by 2010 will also be put at risk, they say.

According to the Institute for Fiscal Studies (IFS), the government will need an increase of between �3 and �5 a week in the new child tax credit - above a planned uprating in line with average earnings - to ensure the target is met.

Fivers all round

The rate of the child tax credit from April 2004 should be announced in the Chancellor's Pre-Budget statement in the autumn.

In the last Budget the Chancellor announced that reducing child poverty will be a key theme for next year's Spending Review.

The Child Poverty Action Group (CPAG) has launched a campaign called "make it a fiver, Gordon", with the aim of getting the government to heed the warnings of the IFS.

"Significant increases in financial support for children have been made but more needs to be done if the ambitious targets to lift children out of poverty are to be achieved," said Martin Barnes, Director of the CPAG.

Since its introduction back in April the Child Tax Credit has been dogged by administrative difficulties.

It replaced three existing tax credits which were available to parents with children and disabled people.

But BBC News Online has received a large number of emails from readers who have become increasingly frustrated by the non-payment of the credit.