What is sensitive personal data, and can it be held on a personal file?

Sensitive data comprises information about an employee's racial or ethnic origins, politics, religion, trade union membership, physical or mental health, sex life, sexual orientation, or criminal (or alleged criminal) activities, proceedings or convictions. Such data must not be held on an employee's personal file without that employee's explicit consent unless the information is necessary in order to comply with the employer's legal obligations. Sensitive personal data volunteered on a job application form or during an interview should be deleted from the employee's personal file, unless retained for legal reasons or in connection with any legal proceedings.