does not include... a member of Parliament in their official capacity
The 1993 Act, which the 2020 Act replaces, included the same exclusion in its interpretation clause.
But why? In its 2011 Review of the Privacy Act 1993 (R123), the Law Commission basicly says "Parliamentary privilege". Requiring MPs to obey the Privacy Principles in their offices might interfere with their freedom of speech in the House, or with the confidentiality of people's communications with MPs (for example, if they communicate with an MP about someone else). But IMHO the first of these is already covered by the English Bill of Rights Act 1688, while the second could easily be handled by exclusions. The fact that Parliament didn't want to consider options those tells us what this is really about: self-interest by MPs, and setting themselves up as being above the same laws that apply to the rest of us. But if this week has taught us anything, its that we need to be protected from them. Exempting abusive, bullying arseholes from the law means we get bullied and abused. And that is simply not acceptable. This exemption should be removed. MPs should not be above the law.