Zac Goldsmith is to lead a "major" anti-Heathrow Airport expansion rally on Saturday (18 November), as the Richmond Park and North Kingston by-election campaign heats up.
The environmentalist quit as a Conservative MP in October over the government's decision to back the building of a third runway at the West London site.
Goldsmith, 41, is now standing as an independent and the Conservatives are not contesting the seat.
"Unlike his Liberal Democrat opponents, Zac has always campaigned against the expansion of Heathrow," a spokesman for Goldsmith told IBTimes UK.
"He believes it would be the wrong choice on environmental and cost grounds – and indeed, the wrong option in every sense.
"His campaign for election as an Independent MP is based on his principle of keeping the pledge to voters, made in 2010 and repeated in 2015, that he would fight plans for a third runway.
"His campaign message is straightforward: Every vote for Zac will be a vote against Heathrow expansion."
Goldsmith is expected to be joined at the Richmond Green rally by actor and former Conservative MP Gyles Brandreth as well as impressionist Alistair McGowan.
Goldsmith secured a majority of more than 23,000 votes at the 2015 general election, but the Liberal Democrats are hoping to build on their success at the Witney and West Oxfordshire by-election in October.
The party was able to secure 30% of the vote and slash the Conservatives' majority by around 20,000.
Liberal Democrat hopeful Sarah Olney, 39, told IBTimes UK that Brexit had been a big issue around the consistency after 69% of Richmond-upon-Thames residents vote Remain, while Goldsmith campaigned for Leave.
"We started our campaign talking about Heathrow, but what was coming to us very clearly from the doorsteps was what people were very much more upset about was Brexit," she said.
"That's why the election is becoming about Brexit rather than Heathrow."
The Green Party have decided not to contest the by-election in a bid to boost Olney's support, while Ukip are endorsing Goldsmith and not fielding a candidate.
Author, journalist and transport expert Christian Wolmar is fighting the seat for Labour. The vote will be held on 1 December.