The former leader of Norfolk County Council last night quit as chairman of the Conservative group at the end of a remarkable day of drama at County Hall.

Derrick Murphy announced he would not be seeking a return as leader within hours of being found to have breached the councillor code of conduct by asking a political assistant to lie on his behalf.

A new chairman of the Conservative group will now need to be elected – potentially triggering a leadership battle just a few months before May's elections.

Meanwhile, the eight-hour public meeting of the council's standards committee heard a series of revelations, including its chief executive David White telling how he secretly recorded a conversation with Mr Murphy.

Last night, Mr Murphy emailed fellow Conservative group members to say he was stepping down as chairman of the group because it would be 'incompatible' with 'a number of important issues' he needed to pursue against the council.

He said: 'My first loyalty has always been to the Conservative Party and the last thing I would like to see is for me to become an issue in what will be a very hard-fought election.'

Earlier, Mr Murphy had been cleared, by a committee of fellow councillors, of six of seven claims he had breached the council's code of conduct, but on one count he was found to have committed a breach.

That one count related to him bringing his office into disrepute because he had asked Kevin Vaughan, a political assistant to Mr Murphy's Conservative group to claim it was so-called twin hatter councillors - county councillors who also serve on West Norfolk Council - not Mr Murphy, who asked him to send an email to the BBC.

The committee imposed three sanctions: A letter of censure will be sent by the committee to Mr Murphy; a report of the breach will be made to a meeting of the full council and Mr Murphy will be required to undergo training in ethics and standards.

Mr Murphy, who had pushed for the hearing to be held in public, previously said he was confident he would be exonerated once the facts were known.

But the biggest revelation at the hearing surrounded the secret recording made by council chief executive David White, as part of an investigation into that email.

The email was sent by Kevin Vaughan, the political assistant to the Conservative group at County Hall, to BBC Radio Norfolk, in April last year.

It was sent two days before Nick Daubney, leader of West Norfolk Council, was due to appear on Nick Conrad's show to discuss the King's Lynn incinerator, which has long been a source of tension between West Norfolk and Norfolk County Council.

It suggested it might 'be pertinent information' for the broadcaster to know that the borough council leader was facing 'a serious leadership challenge' and that his authority had failed to procure alternative technology to the plant.

When the email came to light it sparked an independent investigation at County Hall, which concluded in the summer that Mr Vaughan had acted on the wishes of leader Mr Murphy. Mr Vaughan later left the council, with a pay-off.

Following the independent report, seven people complained about Mr Murphy's behaviour and the county council asked Jenni Richards, QC, an expert in local government, to investigate.

She concluded Mr Murphy should face the standards hearing, with her investigation finding he had asked Mr Vaughan to lie about who asked him to send the email and, in conversations with the council's chief executive about the issue, Mr Murphy 'gave answers that were misleading, evasive and lacked candour'.

That, she said, meant he did not treat Mr Vaughan with respect, amounting to a breach of the councillor code of conduct and bringing his office and the council into disrepute.

But the committee, having heard Mr Vaughan himself speak of his admiration for Mr Murphy and that he did not feel disrespected, concluded he had not been treated disrespectfully. A major revelation came when Mr White told the hearing that, on April 27, he had secretly recorded the conversation he had with Mr Murphy about the sending of that email.

Mr White had told the hearing he had recorded that conversation and had part of it transcribed because he had feared further down the line it could be his word against Mr Murphy's.

Mr White said he had done so because: 'In a nutshell, I felt he regularly tried not to respond to questions I asked and which I felt required answers. He was often very reluctant to give straight answers and was extremely evasive, being difficult to pin down.' Mr White, who recently said he was taken redundancy at the council because he did not have the skills to help make it more commercial as part of a strategic review, said taping his conversation with Mr Murphy had given him no pleasure, but that he thought it was important to have an accurate record, as Mr Murphy often spoke 'in riddles'.

He said he realised that recording the conversation could have a 'major impact on the perception of how the county council is run and its reputation'.

But he said: 'While others might judge that not to be in my own personal interests, I felt the interests of the authority must come first.'

Mr Murphy's solicitor Richard Cassell had accused Mr White of being a 'wholly unreliable witness' and accused him of three breaches of the data protection act, questioning what sort of message it sent to other council workers that he was prepared to secretly record people.

Mr White said: 'I did feel that the reputation of Norfolk County Council could be seen to be on the line and as head of the paid service, without fear or favour, or thinking about my own position, I had to take the action that I took.'

When told by Mr Murphy's solicitor that Mr Murphy did not accept that the transcript produced was fair and accurate, Mr White said: 'You have just made my case for me as to why I felt it necessary to take the action that I did.'

However, the committee disagreed with the investigator that Mr Murphy's conversations with Mr White had constituted a breach of the code of conduct, saying the evidence on that was 'incomplete and unclear'.

Following the hearing, Bill Borrett, acting leader of the county council, said Mr Murphy ought not to seek a return as leader. He said: 'Derrick Murphy has done really great work for Norfolk County Council and the people of Norfolk over the time he was the leader of the Council.

'In the light of yesterday's events I am sure that he will do the honourable thing and step down as the chairman of the Conservative group and resign from the cabinet.

'I believe that the best thing for the smooth running of the council at this financially challenging time would be for him to resign these posts and I would support him wholeheartedly.'

But within an hour of Mr Borrett making that statement, Mr Murphy had signalled his intention to stand aside as chairman of the Conservative group.

He sent an email to fellow Conservatives in which he said: 'The hearing raised a number of very important issues which, I feel, I am honour bound to pursue against Norfolk County Council.

'As a result, I think this will be incompatible with retaining my position as chairman of the Conservative group, who decided to temporarily stand down as Leader of Norfolk County Council until the standards committee hearing.

'Therefore, I am resigning as leader and chairman of the Conservative group. This action will necessitate an election of a new chairman of the Conservative Group.'

When asked by the EDP if he would still be standing as a councillor in Forehoe in May's elections, Mr Murphy, who currently represents Freebridge Lynn, said: 'I am quite happy to be a back bencher. You cannot be a leader or chairman when you are planning to do what I am planning to do.'

When asked if that would involve legal action against the county council he said: 'I have got to sit down with people whose knowledge of the law is immensely superior to mine. There were issues raised at that hearing which I felt were extremely serious.'