Milly Dowler disappeared on her way home from school in March 2002

Milly, who was 13, disappeared on her way home from school in Walton-on-Thames, Surrey, in March last year.

Her sister Gemma started teaching her mother how to send text messages after her parents, worried about her safety, constantly called her on her mobile.

The idea has led to the safety campaign, Teach Your Mum to Text.

Her mother, Sally Dowler, said: "When Milly first went missing and Gemma still wanted to go out and about, obviously it was quite difficult to let her go."

'A good way of keeping in touch'

She added: "One way to get round it was to keep texting. It was a good way of keeping in touch."

Now Gemma is urging other families to follow their example at the start of National Personal Safety Week, which is being run by The Suzy Lamplugh Trust and the Metropolitan Police.

Texting is being promoted as a more discreet way for teenagers, who might find their parents' constant telephone calls embarrassing, to stay in contact with people at home.

Milly Dowler's remains were discovered in Yateley Heath Woods in Hampshire, six months after she disappeared. Her killer has not been caught.

Her mother and father, Bob, are attending the launch of the safety week in London on Monday with Paul Lamplugh, the father of estate agent Suzy Lamplugh.

Suzy disappeared after showing a property to a client in west London in 1986.

Her body was not been found and no-one has been charged with her murder.