The museum holds the largest collection of political material in Britain.
Befitting the national museum of democracy, objects related to the fight for the vote make up a core of the collection. The objects are hugely varied. The PHM collection of trade union and political banners is the largest and most important of its type in the world. The museum also houses an internationally significant political archive and includes the complete holdings of the Labour Party and Communist Party of Great Britain. PHM also holds over 95,000 photographic images covering labour history, the Labour Party and more general political history.