Mass staff protests, alleged power grabs, attempts to remove senior officials and months of boardroom wrangling have threatened to destabilise the People’s Vote campaign, an Observer investigation has found.

Feuding inside the campaign to secure a second referendum has seen demands for some organisations involved to be thrown out, according to a series of accounts. Some fear the splits mean that “the people claiming to want to stop Brexit may end up being the ones who let it happen”.

The splits have culminated in a power struggle over control of a future Remain campaign, should a second referendum happen. Many insiders believe senior figures will be dismissed. “It’s civil war,” said one insider. “It’s total hell.”

While several people said day-to-day relations among staff were happy, disharmony broke out in earnest in the spring. A major disagreement erupted over the March for Change, a pro-Remain rally in London in July. The event, set up by a small group of campaigners wanting to embrace a more explicitly pro-Remain stance, caused outrage among some in the People’s Vote headquarters in Millbank Tower. Opponents regarded it as picking “the wrong time, the wrong message and the wrong people”.

Frustrations led staff to sign an extraordinary letter. “This splinter group has confused our supporters, diverted staff attention and resources, disrupted our relationship with our local groups and grassroots activists, as well as seriously damaging morale,” it stated. “Given the differences in strategy, fundraising and data collection, it is necessary to formalise the separation between us.

“We hope our views will be listened to and it is understood why it is necessary to make serious and urgent changes to our organisation and governance … If these matters are not speedily and fully resolved, we fear that a number of our valued colleagues will resign – potentially derailing the campaign at a crucial point, destroying morale and risking adverse publicity.”

The letter remains highly contentious. While some claim almost 60 members of staff signed it, others say some signatories were pressured into doing so, while others later retracted their names or had not seen the text. “There are bound to be differences of emphasis in campaigns,” said one sympathetic official. “Some people decided March for Change was more of an enemy than the Brexiteers.”

Campaign chiefs were also accused of giving too much support to Labour in the European elections, against advice and despite the party’s ambiguous Brexit stance.

However, the most recent warring has centred on the decision by Roland Rudd, the PR guru, to form a new company to oversee a potential Remain campaign. Rudd is the outgoing chair of Open Britain, the most powerful group under the People’s Vote umbrella. The new company, called Baybridge, has several Open Britain directors on its board, including the businessman Richard Reed.

The March for Change in London in July. Photograph: Aaron Chown/PA

Critics describe the plan as a move by Rudd to consolidate his power over a future campaign and oust James McGrory, the director of People’s Vote, and Tom Baldwin, its director of communications. However, allies of Rudd said the company was part of a plan to bring order to the campaign, and that it would have a large board and some directors directly elected from grassroots Remain organisations. They claimed some pro-Remain groups had already signed up.

“The People’s Vote campaign has done amazingly well, but we can’t rest easy because we still haven’t got there,” said a supporter. “We’ve got to be unified and you do that by all being part of one group.”

Opponents of the Rudd plan said that a rival campaign blueprint, drawn up earlier this year by philanthropist Stephen Dawson, was ready to go and should be pursued. It envisages making Michael Heseltine, the former Tory deputy leader, campaign chair and appointing Labour’s Margaret Beckett and former Tory MP Dominic Grieve as his deputies.

Several sources also cited a strategic disagreement, with Rudd wanting to embrace a more pro-Remain position and campaign directors wanting to concentrate on winning over soft Leave voters and wavering Labour and Tory MPs. One figure described Rudd’s group as the “Kensington splinter”, adding: “Whatever he says, Rudd at heart doesn’t understand how another referendum has to be won on the streets of Pontefract, rather than over cocktails in Phillimore Gardens [a premium Kensington address].”

A Rudd ally disputed the description: “Roland spends huge amounts of time trying to win over new supporters, but at the same time, it’s just absurd to pretend that many of our grassroots supporters aren’t driven by a desire to reverse this madness. Their concerns shouldn’t dictate the campaign, but they should be respected.”

Despite the clashes, senior officials still believe a second referendum can be achieved. “We are still very much in the fight,” said one. “We have come so far and we believe we are close in terms of votes in parliament. And if there’s an election and we run a trusted tactical voting campaign, we’re in business.”