The number of children born behind bars has almost doubled since Labour came to power, with new figures showing women prisoners currently giving birth at nearly four a week.

Figures from the Ministry of Justice show that 283 children were born in prisons in England and Wales between April 2005 and July this year, an average of 1.7 a week. But 49 babies were born between April and the beginning of July this year alone, almost four a week, meaning the 2008 total could reach nearly 200 if births continue at the same rate, more than double the 64 prison births recorded in 1995-96 before Labour came to power.

Prison reformers demanded that women should be locked up only in extreme circumstances, saying that keeping mothers and young babies in prison can harm young children and does nothing to cut crime.

The number of women in jail has nearly doubled in the past decade and stands at more than 4,500. Most women are in for non-violent offences, with about a third jailed for theft or handling stolen goods; in 2006, nearly two-thirds served less than six months.