The first dedicated helpline for victims of stalking was launched on Thursday following concerns that the crime is under-reported because victims fear they will not be taken seriously.
Welcoming the new helpline, campaigners warned that stalking is a serious crime that can lead to violence against the victim, including rape and murder.
They estimate there are two million victims of stalking in Britain - more than half of them women.
A survey by the University of Leicester, the biggest of its kind in Europe, found that three-quarters of victims waited until there had been at least 100 incidents before they approached the police.
The confidential phone service, which is funded by the Home Office and private donations, will have one number for callers anywhere in the country and there will be a single point of contact in every police force.
Alexis Bowater of the Network for Surviving Stalking, which will run the service in collaboration with the Protection Against Stalking and the Suzy Lamplugh Trust, said on Thursday: "Of course the first point of contact if you are being stalked should be the police, but some people feel that they can't talk to the police about it and this is where the helpline will come in."
The charity has also critisised police lack of understanding of the crime and has called for a more vigorous implementation of guidelines from the Association of Chief Police Officers on investigating stalking and harassment.
Last year, an Independent Police Complaints Commission report into the Greater Manchester Police handing of Clare Wood, who was murdered by her stalker in February 2009, found systematic failures and a "shocking lack of understanding" about the nature of domestic violence.