Labour peer

Hello, everyone.

Source : BBC
(Facebook executive has 'incurable' cancer)

Lady Mendelsohn also described how she and her husband, Labour peer Lord Mendelsohn, revealed her diagnosis to their four children.

What does "Labour peer" mean?
Thanks.

Labour peer means member of the Labour Party.

And 'peer' there means a member of the nobility in the UK.

a member of any of the five degrees of the nobility in Great Britain and Ireland (duke, marquis, earl, viscount, and baron).

peer - WordReference.com Dictionary of English

A peer in Britain is someone with a title (Baron or higher). Some are hereditary but most are not (these are called 'life peers'). All life peers and some hereditary peers sit in the House of Lords, one of two houses of parliament in Britain. Many peers who sit in the House of Lords (but not all) are members of and align themselves to a political party. These often are often referred to as [party name] peers. Peers who are not members of a party are sometimes referred to as 'cross-bench peers'.

Lord Mendelsohn is a member of the Labour Party who sits in the House of Lords.