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In last year's election, the Labour Party's vote count increased.
Literal
Last-year [of-の] election [at-で], Labour-Party [of-の] vote-count [subject-が] increased.
Straightforward news report. 労働党 'Labour Party' typically refers to the British Labour Party or similar foreign socialist/labour parties; Japan's domestic parties use different names (民主党, 立憲民主党). 票数 'vote count' is a compound (票 'vote' + 数 'number'). で here marks the setting/context of the event ('in the election'), as distinct from the locative 'at a place.'