In a move designed to encourage supporters to donate to the party, Labour publicised an invoice for £114,000 from social networking giant Facebook to the Conservative Party.
It shows the Conservatives spent over £71,000 on the purchase of "email collection" and almost £36,000 on Facebook "likes" among other services, including video. At the same time, Labour claims it spent £7,000.
Iain McNicol, general secretary, said; "The huge sums the Tories are spending on Facebook ads matter because they are buying their way into people's daily lives."
The Conservative Party is expected to outspend Labour 3:1 in the run up to the election, with most spend in traditional media, while Labour leader Ed Miliband has said he will place emphasis on canvassing, with 4 million face-to-face conversations with voters.
Some marketers claim 2015 could be the UK's first fully digital and social media-led General Election, while others, including Richard Huntington, group chief strategy officer at Saatchi & Saatchi, argue "social media is massively overrated" and like "preaching to the converted'.