The Electoral Commission has published political party funding figures for the second quarter of 2011. Trade unions contributed over 85% of Labour’s £3,093,094 donations of which UNISON Labour Link levy payers contributed £385,263 (13%) – making the union the UK’s third largest political donor during the period in question:
http://www.electoralcommission.org.uk/party-finance/party-finance-analysis/party-funding/Q2-2011
