asked Her Majesty's Government:

Whether they would prosecute a civil servant who disclosed information without authorisation about a taxpayer's affair for (a) misfeasance of public office; or (b) a breach of the Official Secrets Act. [HL3409]

The decision on whether or not to prosecute an individual for the unlawful disclosure of confidential customer information is one for the relevant prosecuting authority. The prosecutor is also responsible for determining appropriate charges, which depend on the specific circumstances of the case, and whether or not it is in the public interest.