The database aims to stop children slipping through the net
The introduction of a database of details about every child in England has been delayed for the second time.
The database of children's names, addresses, birth dates and contact details for their doctors and schools, was due to be piloted from October.
Children's minister Kevin Brennan said "some issues" with the system, called ContactPoint, had been identified during internal tests.
He said more tests were needed to ensure the system was "right".
Shadow families minister Maria Miller said ministers needed "to come clean and confirm whether this delay is because children's personal information is at risk".
The database is designed so that health, education and social workers can share information on vulnerable young people to stop children slipping through the net.
In a letter to Barry Sheerman, chairman of the Children, Schools and Families Select Committee, Mr Brennan said ContactPoint was close to deployment.
"However, we have identified some issues as a result of recent system tests which we are working urgently to address."
A Department for Children, Schools and Families spokeswoman said these issues were minor technical ones identified in early testing.
Mr Brennan continued: "More work needed to be done before embarking on the final phases of testing, which includes testing with users."
He said he had therefore taken the decision to postpone deployment until January 2009, he said.
"I am sure you will agree that it is both prudent and sensible to take a little more time to ensure the system is right," he said.
But Ms Miller said: "We repeatedly warned the government of the problems with ContactPoint but they pressed ahead regardless, ignoring our calls to allow time to sort them out.
"There were clear indications in February of significant security concerns with this database.
"Only now, with just weeks to go until the project is supposed to go live, have they finally agreed to pull back to try to iron out some of the problems.
Lib Dem Children's spokesman David Laws said: "Instead of delaying the launch of the database, this intrusive project must be scrapped altogether.
"A recent independent review has already undermined all of the government's assurances that the database will be secure. The discovery of further technical issues does not bode well for the future."
Government officials have insisted the database would be secure but a report in November 2007 by Deloitte and Touche said it could never be secure.
It identified "a significant risk" to ContactPoint from the security procedures of local councils and other organisations accessing the database.