While manifestos might not strictly be considered an official publication, they serve a similar purpose and can be instrumental in understanding the political landscape. Manifestos (and their international equivalents) are scattered throughout the web and libraries in Cambridge. This page will show you how to access party political manifestos past and present.
There is no single collection of political party manifestos in Cambridge, but there are several scattered throughout the different libraries. For specific manifestos, search the name of the party and year of publication along with a keyword (like 'manifesto') in iDiscover. The manifestos of the three major political parties have been collected in books which are held in the University Library and elewhere:
The University Library has a small collection of material related to the 2016 UK Referendum on membership of the European Union. The collection consists chiefly of campaign materials produced by the various groups on both sides, both in the run-up to the referendum and afterwards. It may be consulted in the Rare Books Room.
More information is available here: https://specialcollections-blog.lib.cam.ac.uk/?p=12778