Oxford University has ordered an investigation into how an animal rights group appears to have secured access to the addresses of staff and job applicants.

The inquiry was launched as the group claimed it would write to the homes of several thousand university employees asking for information about people and companies involved in the building of the university's new animal research laboratory.

Concerns deepened as it emerged the group appeared to even be able to write to people who had submitted job applications.

The Oxford Times, the Mail's sister paper, alerted the university after receiving details from a reader who had applied for an administration post.

Although the applicant was unsuccessful a letter did arrive claiming to be from the Oxford University Information Appeal.

The reader said: "I am not in favour of animal experimentation, but I am even less in favour of the activities of so-called animal rights activists and their tactics of intimidation. There is also the misuse of data under the Data Protection Act to be considered."

The letter requested information regarding the university and its use of animals in research. It began: "I am writing to you as I suspect you are an employee, or student, of Oxford University. I am sure you are aware of the university's plans to build an animal research laboratory in Oxford.

"I am asking for information on contractors working on the new laboratory, individuals involved with the new laboratory, information on the locations and activities of any existing laboratories or breeding facilities and any information, no matter how sketchy, you have relating to animal research."

A university spokesman said it was unclear how the group had acquired personal details.

She said: "We understand a number of individuals have received letters claiming to be from the Oxford University Information Appeal. We take the protection of personal data extremely seriously. The matter is currently under investigation."

Work on the unfinished biomedical research laboratory in South Parks Road ended in July with construction workers complaining of intimidation and harassment from animal rights activists. The university said work would resume in the near future.

Last year, addresses and phone numbers of university staff were displayed on an animal rights website but they were removed by the service provider after protests by the university.

Robert Cogswell, spokesman for Speak, which successfully closed down an animal research centre in Cambridge last year said he knew nothing about the letters.

"This is nothing to do with Speak. We encourage our supporters to work within the law."