The Home Office said that errors at the Criminal Records Bureau were "regrettable" after it emerged that hundreds of innocent people had been wrongly branded as criminals. Almost 700 applicants for jobs in teaching, nursing, childminding and volunteer work were falsely accused of wrongdoing by the government agency set up to protect children. In recent years the number of checks undertaken annually has nearly doubled, from 1.5 million five years ago to almost 3 million last year.

It was disclosed last night that incorrect information was issued for 680 people in the year to February 2008. David Ruffley , a Shadow Home Office Minister, said that the mistakes were evidence of an "emerging crisis" in the handling of public information.

A Criminal Records Bureau (CRB) spokesman said: "The Criminal Records Bureau's first priority is to help protect children and vulnerable adults, and we will always err on the side of caution to help ensure the safety of these groups.

"Since 2004 the CRB has stopped 80,000 unsuitable people working with vulnerable groups with a disclosure accuracy of 99.98 per cent. The CRB is acknowledged as an improvement on previous checking arrangement, although checks which do not correctly reveal a person's true criminal record are still clearly regrettable."

Two years ago, David Davis, then Shadow Home Secretary, branded the Home Office the ministry of incompetence for a similar blunder in the CRB, which led to 1,500 innocent people being branded with convictions they did not have. The error occurred in the cross-checking of names, which meant that members of the public were wrongly blacklisted as pornographers, thieves or violent robbers, in some cases resulting in them being rejected for jobs or university places.

It also emerged that the CRB's 450-strong staff claimed more than 5,000 sick days last year, working out at around two weeks per person.