The bus, which will hit 33 towns and cities across the UK in the next week, claims Brexit's price will be too high.
At the scene today were a whole host of Remoaners - including anti-Brexit campaigner Gina Miller and pro-EU MP Chuka Ummuna.
Britain is due to leave the European Union in just over a year.
The main political parties agree that the decision can not be reversed.
But now a new anti-Brexit political party, 'Renew' - inspired by the French president Emmanuel Macron's En Marche movement.
The bus is a direct response to Vote Leave's red campaign bus during the referendum, which stated there would be £350million extra after Britain left the EU, and it could be spent on the NHS instead.
"We need to knock down this idea that the people were fooled. The 17.4m didn't vote Leave because of a dodgy slogan on a bus. They voted Leave because the laws that govern this country should be made in this country." #Brexit pic.twitter.com/uhqy1xrmmy— thebrexiteer 🇬🇧 (@BrexiteerGB) February 18, 2018
"We're trying to offer a new vision for the future" says @sandrakhad, principal of anti-#Brexit political party @Renew_Britain which has launched a campaign to keep UK in EU. pic.twitter.com/ZBgi6atbVB— RT UK (@RTUKnews) February 20, 2018
The figures they have used are based on leaked analysis earlier this month which said it was going to hurt Britain whatever happened after Brexit.
It suggested that even if we did get a trade deal, growth would be down 5 per cent in the next 15 years - which campaigners say equates to £2,000 million per week.
But those were based on gloomy predictions from civil servants, and didn't take into account the bespoke deal the Prime Minister is trying to get, Brexiteers argued.
Sandra Khadhouri, James Clarke and James Torrance deliver the launch of the "Renew" anti-brexit political party during a press conference at the QEII Centre in London, Monday, Feb. 19, 2018.
Renew is a newly registered political party set up by a group of independent candidates who stood in the June election 2017 on a campaign to rethink Brexit.
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