Maternity services have accounted for nearly half of the value of clinical negligence claims against the NHS since 1995.
The Royal College of Midwives said the figures showed that failing to invest in safe and well-staffed services was a false economy.
Claims under the clinical negligence scheme for trusts relating to obstetrics have amounted to£946.5m of a£2.2bn total, NHS Litigation Authority figures show.
The college accused the government of "yo-yo funding", which it said could lead to unsafe services.
Figures released to Parliament show spending on acute maternity services in England fell from£1.68bn in 2005-06 to£1.62bn in 2006-07, then rose again to£1.79bn in 2007-08.
Royal College of Midwives deputy general secretary Louise Silverton said funding in some regions was even more erratic and had failed to keep pace with the rising birth rate.
"We have seen spending on maternity care in some regions yo-yoing in recent years," she said.
"In the South West, there has been a dramatic and relentless 17 per cent increase in the number of live births over six years, but it has had a yo-yoing in maternity care funding.
"There was a huge cut in spending on maternity services of£27.5m for 2005-06 to 2006-07, but there was a£36.2m increase in funding from 2006-07 to 2007-08.
"This cycle of deep cuts in funding followed by a sudden splurge in funding is like a year of financial drought followed by a funding flash flood. People running maternity services need certainty in funding to plan services."