Unite has boosted its relationship with Jeremy Corbyn’s team by recruiting one of his key lieutenants.

Anneliese Midgley, Jeremy Corbyn’s deputy chief of staff, has been appointed as political director of Unite, Britain’s biggest trade union.

Midgley, who helped organise Corbyn’s leadership campaign over the summer, has served as deputy to Simon Fletcher since September. She will start her new role in the next few weeks, replacing Jennie Formby, who moved to be the South East Regional Secretary last month.

Midgley has a reputation for being a pragmatic campaigner and was previously Unite’s head of political strategy before joining Corbyn’s team.

Fletcher, who also worked with Midgley on Ken Livingstone’s unsuccessful 2012 London mayor bid, said the move brought he party closer to the trade unions.

“Anneliese has done a fantastic job for Jeremy, first on his leadership campaign and more recently in the leader’s office – but whilst we will miss her, this is both a brilliant opportunity for her and a further cementing of the party’s relationship with the wider labour movement. We will be seeing a lot of her in her new role,” Fletcher said.

“Anneliese will be taking up her new job soon and also continuing to work with us here to ease the office through a transition and to contribute to our work on the referendum.”

A spokesperson for Unite said the trade union did not comment on staffing matters.