Rosemary Archer will now quit her role at the end of this month, instead of March next year as previously planned.

Ms Archer, who became Leeds's first director of children's services in 2006, announced her retirement in October – weeks after Ofsted inspectors delivered a damning verdict on the work of the Leeds City Council department.

The watchdog found vulnerable children had been placed at risk of abuse and neglect because of council failings.

And a serious case review following the rape and murder of Gipton toddler Casey Mullen found the authority failed to carry out an assessment that could have prevented her death.

This month Ofsted announced Leeds children's services was performing poorly and not meeting minimum standards.

The council said the recruitment process was under way to find an interim director and the permanent position would be advertised in the New Year.

Ms Archer, who is in her late 50s and paid around £113,000 a year, said: "Any interim arrangement must be able to take forward, at pace, our plans for improvement and so should be in place as soon as possible.

"I have decided the best way to do this is to bring forward my leaving date from March 2010 to December 2009.

"We recognised and fully accepted the findings of the unannounced Ofsted inspection in July this year and since then have undertaken a huge amount of work to drive forward improvements and this work will continue."

The position of director of children's services was created by the Government in response to the death of Victoria Climbie, after the chief executive of Haringey Council said he did not feel personally responsible for the youngster's death.

Coun Stewart Golton, executive board member responsible for children's services, said:  "Rosemary has worked hard to improve the lives of vulnerable children, young people and adults in Leeds."

Bill McCarthy, Yorkshire and Humber NHS chief executive, was appointed this month to chair an Improvement Board to oversee changes to children's services, which will report back to the Department for Children, Schools and Families.