Change UK will launch its campaign later for the European Parliamentary elections on 23 May.
The party – formerly known as The Independent Group – is made up of 11 MPs who quit Labour and the Tories.
They are preparing for the vote as the latest Brexit delay means the UK may have to take part.
Change UK interim leader Heidi Allen said the party – and its 70 candidates across the country – would be the “natural home” for Remain voters.
Ahead of the launch in Bristol, she told BBC Radio 4’s Today programme the candidate list was made up of former members of the Tories, Labour, Liberal Democrats and Greens – as well as some non-political individuals – and people were starting to call them “the Remain Alliance”.
A number of parties have begun launching their campaigns for the European Parliamentary elections after Theresa May agreed a Brexit delay until 31 October with the EU.
Mrs May said the UK could still exit before this date if her withdrawal agreement is approved by Parliament.
But, if not, the country is likely to have to hold European Parliament elections.
Last week, ex-UKIP leader Nigel Farage launched his new Brexit Party, promising that the 23 May vote would be the “first step” on a mission to “change politics”.
‘Beginning of the story’
The Independent Group was formed after eight Labour MPs and three Tory MPs left their parties in February.
The three Conservative MPs blamed “a shift to the right” in their party and the government’s “disastrous handling of Brexit”, while Labour MP cited their party’s stance on leaving the EU, along with the leadership’s handling of anti-Semitism.
In March, the group applied to become a party with the name Change UK and was given approval in April, meaning they could field candidates in the European elections.
Ms Allen described her new party as “a solid pro-Remain, pro-People’s Vote party for people to put their cross against on the ballot paper”.
She said it was treating its first test at the ballot box “very, very seriously indeed”, as the campaign itself would “send the loudest possible message to both the government and the opposition about how people in the UK feel about leaving and the deal that is currently on the table”.
She added: “Later, people will see where [our candidates] come from. Political and non-political, public sector and private sector, people are gravitating towards us.
“This is the beginning of the story for Change UK.”