A third of England's 150 local authorities did not sign off on the first phase of ContactPoint scheme by the planned date of March 13 and staff say faults with the £224m system place both children and social workers at serious risk.

ContactPoint was set up in 2003 after Lord Laming's report into the death of Victoria Climbie and stores every child's address, medical and school details for use by staff in education, health, social care, youth justice and the voluntary sector.

In January, around 300 council workers began "shielding" details of an estimated 55,000 children, including children fleeing abusive homes and those of celebrities and politicians.

But some staff were alarmed to discover adopted children are listed by both their original and their adopted surnames, allowing them to be tracked down by their birth parents.

Checks revealed unprotected duplicates had been generated automatically from central government data. In one council, a vulnerable child's record was duplicated six times.

Liberal Democrat shadow minister for children Annette Brooke called it "a bombshell".

She said: "It is deeply concerning that after taking so long to roll the system out, the Government has still failed to spot these major problems.

"If children have been removed from abusive homes they should be kept entirely safe from being traced. We cannot have some of our most vulnerable children being put at risk in this way.

"This is an absolute bombshell and confirms all of our worst fears. The roll out of this flawed database now needs to be stopped."

The Department of Children, Schools and Families had hoped to get the database running in 17 "early adopter" authorities in March, but the project has now been held up until all councils sign up to the shielding process.

The department has halted the automatic flow of data into ContactPoint from central Government, such as the school census and the child benefit database, until they can be sure no more unprotected duplicates will be created. A spokeswoman said the database will not be brought into full use until the problems have been resolved.

"We are aware of the issues raised and are tackling them, working closely with local authorities. We will not extend ContactPoint to all local authorities until we, and they, are satisfied that these issues have been addressed," she said.

Despite the security problems every council in Yorkshire signed off by March 13.

Harrogate and Knaresborough MP Phil Willis said he was "astounded" by their decision, and called for every council to withdraw from ContactPoint until the problems are solved.

"The fact that no Yorkshire council has picked this up demonstrates a lack of competence," he said, adding: "They should immediately retract their position on shielding and adopt a position of non-compliance until these problems have been resolved by the Government."

Craig Whittaker, councillor for children's services at Calderdale, said: "At the end of the day, this is just going to place social workers at much greater risk and they are already taking a lot of flak.

"These are people who are in the front line and anybody who has the ability to trace a child is clearly going to pose a great risk to children and to social workers."

Tim Loughton, Shadow Conservative Children's Minister, said: "The Government has proved that it cannot be trusted to set up large databases or to keep our data secure.

"Despite serious and widespread concerns about the security, integrity and necessity of this database, ministers seem determined to bulldoze it through.

'If ministers believed ContactPoint was secure, there would be no need for shielding."