Zac Goldsmith has one of the most anti-European Union voting records in the Commons figures show.
The former Tory Richmond Park MP has resigned his seat in order to fight a by-election in protest at the government’s decision to expand Heathrow.
The Liberal Democrats believe they will be able to capture the seat from him by making the race about Brexit.
Goldsmith campaigned for the UK to leave the EU. However 79% of voters in Richmond Park voted Remain.
Figures from public whip website, which tracks the voting record of MPs, show Goldsmith voted in favour of the EU only 35% of the time. The only other leading Brexiteer to have a more anti-EU record was Brexit secretary David Davies with 32%.
Lib Dem leader Tim Farron said: “This election is a clear referendum on Brexit and the choice is clear - between Zac, the Hard Brexiteer endorsed by Farage and UKIP or the Liberal Democrats.
“This election is about how the government is handling Brexit. I believe the government don’t have a plan or frankly, a clue. We need to be in the Single Market and to protect jobs.
“The best way to send to a message on Brexit and Heathrow is to vote Liberal Democrat on December 1st. That result will send shockwaves through Downing Street.”
Yesterday Nick Clegg said Richmond Park voters should reject Goldsmith as a “hip, faintly glamorous, minor royal” and elect Lib Dem candidate Sarah Olney.
The figures from public whip show international trade secretary Liam Fox had a much more pro-European voting record than Goldsmith. He voted for the EU 45% of the time.
Boris Johnson is on 41%, Michael Gove on 42%, Ian Duncan Smith on 45%, Andrea Leadsom on 64% and Priti Patel on 66%.