Lack of support for grandparents who look after their grandchildren as carers has been highlighted in research by Labour MP Frank Field.(1)

He found that many grandparents who performed a caring role were doing so because the parents were unable to cope, whether due to substance misuse or relationship problems.

Jean Stogdon, chair of charity Grandparents Plus, believes there are "several hundred thousand" grandparent carers but says there is no official figure as the question is not asked in the census as it is in the US.

This form of kinship care saves the taxpayer tens of millions of pounds, but the government is accused of doing too little to encourage and support it.

Professionals say the financial support available to grandparents can depend on luck and where you live.

The commonest form of support is the residence order allowance, worth about £60 a week, but which is at the discretion of councils and lasts until the child is 16. Grandparents must apply for it at a residence order court hearing.

Another option is to become a foster parent. But some grandparents are reluctant to go down this route, despite allowances of up to £200 a week, because it requires social services to start care proceedings.

"Those who become foster carers get much better support," says Robert Tapsfield, director of charity the Fostering Network. "Which route you go down depends more on luck than need. If a child is subject to court proceedings and fostered with relatives they are entitled to financial support, but if grandparents step in before that they often get nothing."

Some grandparents are starting to use the system to their advantage, says Stogdon. "What grandparents are sussing out is if they leave a situation until it becomes a crisis they will get more money - if they wait until the child is placed with them they will get better support."

There are other forms of financial support available: pensioners can apply for child tax credits and child benefit, working grandparent carers are eligible for working tax credits, and income support and council and housing benefits can also be claimed. On top of this, social services can provide the over-60s with a £1,000 community care grant in times of exceptional hardship.

However, many grandparents still claim nothing, putting extra pressure on them, says Linda Nunn, advice line manager at grandparents charity the Grandparents' Association.

"Many struggle because their only income is a pension," she says. "A number of people have said they have been forced to go back to work because they can't get the allowances they need. Others won't take on a child because they can't afford it."

The government says offering financial support to kinship carers is interfering too much in family life. But Bob Broad, professor of children and families research at De Montfort University, accuses ministers of using this as an excuse to "exploit" grandparents.

"Grandparents do it despite not getting enough support," he says. "They do it because of the emotional bond which the authorities tend to exploit. There is no commitment from the government."

Broad says studies show that children looked after in kinship care do as well, if not better, than children taken into formal care settings, and he believes the government should change the system so that financial support is tied to the child's needs rather than who cares for them.

Nunn says: "If the government put more money in, more people would be prepared to offer kinship care and there would be fewer children in state foster care."

1. Britain's Pensioner Parents: The Quandary of Parenting your Grandchildren, Frank Field, June 2005.