The councillor overseeing improvements to Northamptonshire's under-fire children's services is stepping down, the county council said.
A report last year found that children in care were suffering due to "systemic failings".
Catherine Boardman, a Conservative, is not leaving because of the department's problems, the authority said, but to concentrate on running her family farm.
A successor to her role is likely to be announced on Thursday.
Ms Boardman was appointed cabinet member for children and education in 2013 having served six years on the children's scrutiny panel and four years on the adoption panel.
'Turned a corner'
Her role was to oversee improvements outlined by watchdog Ofsted, which said "key shortfalls" within health, education, employment and training had adversely affected the outcomes for vulnerable children.
But her decision has taken "everybody" at the council by surprise, with the authority currently one year into a two-year improvement programme, BBC Radio Northampton's politics reporter Willy Gilder said.
Concerns over delays to service improvements had existed since Kevin Crompton, appointed as chairman of the local safeguarding children board to overhaul the service, left at the end of February.
It was understood that some improvements had already been made, with inspectors saying they thought the service had "turned a corner", but Ms Boardman's exit would still come as a "blow" to the council, Mr Gilder said.
Despite budgets being slashed at the authority this year, children's services has been given an extra £12m to aid the improvements.