A group of anti-Tory activists have launched a campaign to get people living in houseboats in marginal constituencies to register to vote.
Votey McVoteface has set up a website in a bid to overturn seats in London, Bristol, Leeds, Milton Keynes and Nottingham with narrow Tory majorities.
Founder Sam Lund-Harket said it was not affiliated to any political party.
But Electoral Commission (EC) said boaters and those of no fixed address should register on its website.
Votey McVoteface is targeting seats that saw Labour or the Liberal Democrats come second in the 2017 general election.
Data use 'concerns'
Southampton Itchen has been cited as an example where in 2017 the constituency was won by a Tory MP with a majority of just 31 votes over Labour.
Other waterway constituencies include Jacob Rees Mogg's North East Somerset and Anna Soubry's, now of Change UK.
Although Rees-Mogg had a healthy majority in 2017 of more than 10,000, Soubry won Broxtowe for the Conservatives with a majority of 863 over Labour.
Despite the group's anti-Tory stance, Ruth Westcott, who lived on the river in London for three years, said its main aim was to extend voter participation.
"But we have to be honest about how we feel about Tory policies over the past 10 years.
"It would be disingenuous to be impartial," she added.
A Conservative party response to the campaign said: "We would encourage everyone to register to vote to have their say in the election, no matter where they reside."
A Canal and Rivers Trust survey in 2016 of 3,675 London houseboat dwellers found just over half of its 1,323 respondents used their houseboat as their primary home with 50% of those saying they chose to due to affordability.
The EC said its most recent number of people registered to vote with no fixed address is 2,963.
It added it was "concerned" about the group's "use of people's data".
Mr Lund-Harket, who lives on a riverboat in east London, said they did not scrape anyone's data for use by third parties, nor was it able to see or store the information.
"After completing the form on our website you download it as a PDF to email or post it to the electoral officer.
"We don't have cookies on the site so cannot gather information ourselves."
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