Can data protection concerns justify failing to inform or consult?

No. HR departments sometimes express concerns about data protection and commercial sensitivity when faced with statutory consultation obligations, but the Data Protection Act 1998 (DPA) does not prevent an employer supplying this information to unions, because it is supplied under a legal duty. Employers must comply with the DPA when handling the information, in particular by ensuring it is accurate, up-to-date and secure.

The Information Commissioner has published guidance on data protection good practice in connection with TUPE.

Employee information supplied to reps in connection with business sales can sometimes fall outside the scope of the statutory duty imposed by TUPE. This is the case, for example, where there is a share sale, where TUPE does not apply. The ICO guidance recommends extra safeguards such as anonymising information where possible, seeking employee consent, and agreeing special terms for the protection of the information.

http://ico.org.uk/for_organisations/data_protection/topic_guides/~/media/documents/library/Data_Protection/Practical_application/GPN_DISCLOSURE_EMPLOYEE_INFO_TUPE_V1.ashx