Advanced plans for another centrist political party to be launched after Brexit were developed by MPs earlier this year, it has emerged.

Dozens of figures from inside and outside Westminster were involved in the project, designed to go public once a second Brexit referendum was no longer possible.

Nick Boles, the former Conservative minister who quit the party over Brexit in April, said he had been “constantly” in talks about a possible new party and had at one point been confident it would happen. An earlier failed attempt to launch a new party, Brexit delays and the tantalising prospect of a second referendum had stopped it.

“It’s almost all I’ve been doing,” Boles said. “I can’t mention names, but it involved some very seriously good people, both MPs and not MPs, but people of great ability, experience and commitment. We had everything in a sense, except for the final resolve of a sufficient number of the individuals we needed in the Labour party. Without that, we were never going to get anywhere.

“If you’d asked me a few months ago, I would’ve been very optimistic that by now, something would’ve been up and running. Probably I deluded myself. Because I had made the break, and because I hadn’t thought about it for a very long time and did it in stages, I somehow assumed that it was easier for others to take the same journey than it is. What I’ve realised is that it’s a very difficult journey.”

Boles, who is standing down as an MP at this election, said the project could only have succeeded if Brexit had been secured, allowing those wanting a soft Brexit and those wanting a second referendum to unite.

“We all thought that something new would only work and should only launch after this first phase of Brexit had been resolved,” he said. “As soon as you’re out of the EU, then we’re all totally agreed – which is that we want the closest possible relationship with the EU. But the referendum idea came along and split us in two.”

He said the failure of the party of 11 MPs launched in February, initially under the banner of The Independent Group (TIG), damaged public appetite for a new party. Initial success evaporated after the group changed its name and struggled with a lack of organisational strength.

“It was a jumping of the gun on a process that had begun but hadn’t matured,” he said. “Because TIG happened too soon and screwed it up, that gave those who were more nervous about the idea an excuse not to [split].

“It’s not impossible that Theresa May’s Brexit deal could have got through parliament, maybe at the second time of asking. Then I think, a potential second attempt at creating something new might easily had happened, and might even have been more likely than not.”

While it was not impossible such a force could happen from within parliament, Boles said it could actually emerge as a campaign outside Westminster. “The question for people like me is, I guess, is that it?” he said. “Throughout the process where I was having these conversations and planning meetings with various others mainly in the Labour party since I left, a number of people said to me, ‘Nick, I admire what you’re trying to do, I wish you all the success, but this is not how it is going to work’. It will work if it’s a genuine, grassroots political movement that gathers force and takes parliament by storm - and erupts into an election cycle.

“It won’t be something that is made up of a bunch of MPs elected for some other party and [who] for various reasons became disenchanted and created a liferaft to clamber aboard. I must say, while it’s very hard for a movement of that kind to succeed, I sort of buy the argument that that is how it’s got to happen.”