The former children’s commissioner and Labour peer Anne Longfield will chair the national grooming gangs inquiry.

Her appointment is to be announced by the home secretary, Shabana Mahmood, after a long-delayed search during which some victims quit the inquiry’s advisory panel amid disagreements over the chair appointment.

Louise Casey, who was asked by the prime minister to help re-establish trust in the inquiry, said in a letter to the remaining survivors helping the inquiry that she hoped the chair would have the qualities they were looking for.

Casey, who carried out a nationwide audit on the grooming gangs that recommended a full inquiry, told the survivors in her letter she hoped they would have the opportunity to meet the chair and panel this week, and promised to stay involved in the inquiry.

Earlier this year a group of women quit the inquiry’s victim liaison panel, accusing the government of attempting to widen its remit to consider other forms of child sexual abuse.

Several demanded the resignation of the safeguarding minister, Jess Phillips, though a number of other women on the panel then wrote to defend Phillips.