Jeremy Corbyn’s chief of staff, Karie Murphy, is being seconded to Labour headquarters to lead the party’s election efforts in the wake of a series of clashes over strategy and management style.

Murphy has long been a core member of Corbyn’s team, together with his head of communications and strategy, Seumas Milne.

Corbyn’s political director, Amy Jackson, will join Murphy in the party’s Southside HQ in Victoria, central London – and the Guardian understands at least one other key staff member from the leader’s office is leaving.

Labour played down the significance of the shakeup, with a source saying “as we ramp up campaigning ahead of a general election, we are maximising the use of the resources we have to ensure we are successful. Karie will drive this crucial work from HQ, as she did during the last election.”

But Corbyn’s close allies Diane Abbott and John McDonnell had been urging him for some time to move Murphy out of her powerful role in the leader of the opposition’s office.

She and Milne were regarded as brakes on the party’s gradual shift towards advocating a second Brexit referendum.

And when Corbyn’s policy chief, Andrew Fisher, resigned last month, in a blistering letter that was leaked to the Sunday Times, he complained of what he called the “blizzard of lies” emanating from the leader’s office.

Two senior party sources told the Guardian they believed it was Fisher, who is very close to Corbyn, who had finally convinced him a shakeup was necessary. One shadow cabinet ally said the Labour leader, who tends to avoid confrontation, had “screwed up his courage” to make the move.

Tensions have been running high since Labour’s conference in Brighton last month, which kicked off with a botched attempt to abolish Tom Watson’s job of deputy leader.

The putsch against Watson was initiated by the Momentum chair, Jon Lansman, but he told friends it had the approval of Corbyn’s office, and Murphy was widely believed to have known about it in advance. The Guardian understands the Labour leader later remarked in private that it made them look like student politicians.

Murphy – a former nurse who is a close friend of the Unite general secretary, Len McCluskey – played a key role in coordinating the 2017 general election campaign.

She has a reputation for being combative, though allies insist she is simply an effective manager.

Labour members – and some shadow cabinet ministers including Emily Thornberry and Keir Starmer – had hoped last month’s conference would shift the party’s policy decisively towards supporting remain at a future referendum.

But Corbyn, his advisers, and key members of the national executive committee (NEC) held out against that shift, fearing it would damage the party’s electoral chances in leave-supporting seats.

It is unclear whether Murphy would return to her chief of staff role in Downing Street if Labour wins a general election, which could come within weeks.

Some of Corbyn’s allies are already beginning to think about what might happen if he loses, and is forced to resign – with favoured candidates, including Rebecca Long-Bailey and Laura Pidcock, being given increasingly prominent roles.