By Reevel Alderson
BBC Scotland Social Affairs Correspondent
A quarter of families in Scotland were found to live in poverty
The Scottish government has been urged to change the way it tackles the problem of child poverty.
A series of studies it has published reveals poverty may be more serious for many families than had been previously believed.
Researchers with Growing Up in Scotland, who tracked the experiences of 8,000 families, said a quarter of children were "persistently poor".
They said government measures to deal with the problem needed to be targeted.
Eradicating child poverty is a commitment of both the Westminster and Holyrood governments.
Thousands of families
Scottish government figures suggest 90,000 children were lifted out of poverty between 1998 and 2005 - although some commentators predict a commitment to end child poverty by 2010 will fail to be met.
It is widely recognised poverty can have negative effects on children's future lives.
But despite a range of initiatives, the Scottish government's latest estimate is that 20% of children live below the low-income threshold, calculated at £17,000 a year for two adults living with two children or £13,000 for a lone parent with two children.
But researchers on the Growing Up in Scotland programme, which has been tracking children of 8,000 families since 2005, said the figure was actually higher - they calculate it at 24%.
They said: "Poverty touches more Scottish children than standard estimates may imply."
In particular, they said many of those in poverty were "persistently poor", but added: "There are no concerted measures to tackle persistent poverty above those designed to tackle poverty in general."
Other research reports published by the Scottish government included the effects of diet, unemployment and health as contributing to poverty.
Researchers said being without work, and in particular regular work, was a key influence on poverty.
But they admitted families without work were also likely to experience a range of other disadvantages - including low education and poor health, and often required quite complex childcare arrangements to be able to work.
They said employment policy needed to operate alongside policies designed to contend with these other hardships.
Scottish Public Health Minister Shona Robison said the government has a vision to give children the best possible chance in life and tackle Scotland's historic legacies of poverty, poor health, poor attainment and unemployment.