County council leader Keith Mitchell is set to step down after 10 years in the job.

The Conservative councillor wrote to party members over the weekend to inform them of his intention to resign in May.

He has led the county council for a decade and the Conservative group at County Hall for 12 years.

In the letter he told party members he believed it was the right time to step aside.

He said: “On 5 November 2011, I complete 10 years as leader of the council and 12 years as Conservative group leader.

“While Margaret Thatcher is my political hero in almost all respects, I have always had a sneaking respect for Harold Wilson’s sense of timing.”

Mr Mitchell, who became a county councillor for Bloxham in 1989, is set to formally announce his decision today and will then step down at the council’s annual meeting in May. He told party members he would not be retiring and would look for a “a political or other public-service role”.

In May, we revealed how Mr Mitchell survived a leadership challenge from cabinet member Ian Hudspeth and Thame and Chinnor councillor Nick Carter.

Last night, Mr Hudspeth said: “Keith has done a fantastic job in transforming the county. The leadership issue will be sorted out next April.”

He would not confirm if he would stand.

Last night Mr Mitchell said on his blog: “My reason for making the position clear now is to give my Conservative colleagues plenty of time to consider the issue of succession as Leader of the Conservative Group and, therefore, as Leader of the Council. ”

He said he was not retiring: “I will see what is out there once I step down from the very demanding job of Leader of the Council.”

He also confirmed he would continue as a backbencher until the next council election in 2013.

Mr Mitchell has seen his recent reign dominated by the need to make large cutbacks to council services.

The 65-year-old, who describes himself as “proud to be politically incorrect” on his council profile web page, is no stranger to controversy.

Last week he tweeted about a “gaggle of deficit deniers parading around outside” County Hall.

He added: “Do they have jobs or are they on benefit?”

He has also branded student fees protesters “oiks”, labelling them “an ugly, badly dressed student rabble” and criticised leading authors including Philip Pullman for their opposition to library cuts.