Families were "unique units" and not statistics, Sir Menzies said

The Lib Dem leader said he was shocked to learn this happened - and it was symbolic of uncaring social services.

He also called for an "ethic of care" to protect children, plus measures so adults could enjoy more family time.

And backed national standards for childcare, in a speach to the National Family and Parenting Institute.

Sir Menzies demanded an end to the quirk in the social services system which left children without suitcases.

"What incredible symbolism for young people being moved, no doubt with a certain amount of stress and anxiety, to know the things they value most are put into black bin bags," he said.

'Protect the vulnerable'

The "ethic of care" was the principle that "in a diverse and changing society, we must all recognise a duty to protect the vulnerable, to promote their welfare and to secure their long-term interests", Sir Menzies, 65, said.

Where the state plays a role in family life, it must do what it can to help parents build a stable environment for themselves and for their children Sir Menzies Campbell

"Opportunity should not be an accident of birth. It should not rely on being born into a family that can provide it."

He went on: "We need to give parents genuine choice - the freedom to work if they wish, but also the opportunity to spend more time at home, so they can invest in their family life as well as their professional life."

And while it was not possible to ignore "the financial realities of modern life", work could be more flexible and time spent at home more affordable, he said.

For instance, statutory maternity pay should go up to the same level as the national minimum wage, he suggested.

Sir Menzies demanded automatic mediation for parents seeking a custody hearing in a court, with the courts themselves being less intimidating.

Along with "more appropriate financial support" for close family members looking after children, new national standards for quality childcare - such as an NVQ qualification - were required for anyone caring for under-18s, he said.

"Politicians are not well-equipped to lecture on how people should raise their children," said Sir Menzies, who has no children of his own but whose wife has a son from a previous marriage.

"But where the state plays a role in family life, it must do what it can to help parents build a stable environment for themselves and for their children."

He pledged support for "kinship care", where youngsters were looked after by close relatives, not parents.

He also claimed it should be easier and more affordable for adults to juggle work and family commitments.

Parliamentary debate

In his party conference speech earlier this month, Conservative leader David Cameron said parents of children of all ages should be able to ask to work flexible hours.

And on Thursday, the government rejected Tory calls for a Commons debate on nursery provision.

Shadow Commons leader Theresa May told MPs: "Government guidance means that nurseries cannot charge top-up fees, which means that many private nurseries will probably close, which will cut the availability of childcare."

But Commons leader Jack Straw said: "If I was a Conservative, I should keep very quiet about childcare because of the Conservatives' utterly lamentable record on it."