Hilary Armstrong, Labour MP for Durham North-west, to whom the Cabinet Office document was leaked, said: 'Government rhetoric on lone parents is simply not backed up by evidence from their own advisers.
'Cabinet ministers at the Tory conference used poisonous language to try and scapegoat lone parents for the Government's own policy failures. Cutting benefits will push more families into poverty and put even more strain on relationships with families.'
Ms Armstrong, who is Parliamentary Private Secretary to John Smith, said the report supported Labour's view that the Government should enable lone parents to escape the benefit dependency trap by offering affordable child care.
Sue Slipman, director of the National Council for One Parent Families, said: 'We support a positive campaign of prevention, including sex education and contraceptive supply, to encourage the decline in the numbers of teenage pregnancies, but lowering the age of consent is unnecessary and would open up very young girls to sexual exploitation.'
The Child Poverty Action Group said: 'We are outraged that the Government continues its victimisation of lone parents and is seemingly determined to cut their benefits. The children of lone parents are already living in a greater degree of poverty than those from two-parent families.'
Recent research found Income Support was pounds 23 a week less for a lone parent with two children than was needed for basic necessities. The charity said: 'The most alarming thing about these proposals is that the Government are proceeding with them despite the evidence or its own civil servants that benefits do not provide an incentive to become a lone parent.'
Ian Sparks, director of the Children's Society, said: 'Cutting benefits will only force children further into poverty. It is a direct contradiction of the Children Act which states the needs of the child are paramount.'
The Daycare Trust called on the Government to introduce a national child care policy with better training opportunities for jobless lone parents and changes to the benefits system to help them get employment.
Marion Kozak, the trust co- ordinator, said: 'Many lone parents want to work but cannot afford to because the benefits system ignores their child care costs.
'If the Government seriously wants lone parents to return to work it should improve child care provision and take child care costs into account before taking away benefits.'
Ms Kozak also referred to a recent court case in which Heidi Colwell, a lone mother, was initially jailed for six months for leaving her child at home alone while she went out to work because she could not afford to pay for child care.
'Her case shows that sensible family support such as improved child care provision is essential,' she said.
Ms Kozak was sceptical about forcing grandparents to support the child. 'In many . . . cases the grandparents are already giving all the help they can. Where are they supposed to find the extra money?'
Mary Honeyball, director of Gingerbread, said: 'It is shocking that the Government had this information but continued to spin its moral myths about lone parents being responsible for the crime wave or having babies to get benefits.'