Shelter helped 2,700 families in London in 2002

Releasing the figures, it called on the government to fulfil its promise to end its policy of housing families in bed and breakfast hostels on a short-term basis, by March 2004.

Shelter says constantly moving children from one temporary home to another can affect their emotional and physical well-being.

It says frequent moves mean children are forced to change schools and friends on a regular basis, while damp and cramped accommodation can cause illnesses.

A spokesman said: "These factors have a hugely damaging effect upon the emotional well being of children, often resulting in behavioural problems such as hyper-activity, sleep disturbance and bed-wetting."

Of the boroughs which sought help from Shelter, Hounslow, Camden, Havering, Hackney and Hillingdon, have the highest proportion of homeless families.

The charity's director Adam Sampson said: "Shelter sees thousands of families with children every year who are experiencing the terrible hardship of bad housing and homelessness.

"These families are living at the sharp end of the housing crisis. It's vital that we continue our work if their lives are to be improved."