Four Conservative councillors dramatically resigned from their group at a council meeting tonight over claims of "backstabbing and duplicity" in the party.

The resignations of Councillor Suzanne Evans, for Hillside ward, and Coun Richard Hilton, for Lower Morden, Coun Rod Scott for Raynes Park and Councillor Linda Scott, also for Raynes Park, come after the group elected Councillor Oonagh Moulton on Monday as their third leader in three months, after Coun Hilton called a leadership election last week.

Coun Hilton became Leader just six weeks ago after his predecessor Coun Debbie Shears resigned from the post in March.

Coun Evans, the group’s whip, announced her resignation at the annual mayor-making meeting tonight, and her intention to form a new group based on "integrity and accountability", which all three former Merton conservatives have said they will be joining.

Coun Krystal Miller, for Trinity ward, was set to be appointed Mayor of Merton tonight unopposed, but at the final hour Coun Evans put forward fellow Conservative Councillor Chris Edge for the position.

In a speech, she said: "Chris is a former deputy mayor, an able and long-serving councillor and a respected local businessman.

"There’s no doubt he has the gravitas, the experience and perhaps most important of all, the moral fibre to be First Citizen of the Borough.

"His appointment as mayor is long overdue.

"Twice he’s had the mayoralty stripped from his grasp, thanks to a culture of back-stabbing and duplicity that some members of the current Conservative group appear to have adopted as their badge of honour."

She said Coun Edge was promised the Mayoralty in 2010, but "fell victim to a back-room deal" to ensure Councillor Debbie Shears stood unopposed for leadership of the Conservative group.

She added: "Now it’s proposed he becomes the sacrificial lamb slaughtered on the altar of Councillor Krystal Miller’s political ambition."

She wished Coun Moulton luck in her new role but said: "I cannot give tacit approval to the disgraceful, dishonest and poisonous war waged by nine of your colleagues to put you in the Leader’s seat."

The announcement was met with shock from other councillors, and Conservative leader Councillor Oonagh Moulton, who said she would be supporting Coun Miller as Mayor.

She said: "I have to apologise on behalf of my group over what were two former colleagues of my group, for their actions in putting forward another nominee.

"I'm pleased on behalf of Merton Conservatives to support Coun Krystal Miller."

Labour Councillor Martin Whelton said Coun Miller would be a "fantastic ambassador" for the borough and condemned the politicisation of the mayor making meeting - a sentiment met with applause.

Following a vote, Coun Miller was voted to become mayor of Merton with 53 votes to 4.

Councillor John Sergeant, of the Merton Park Independents, was named deputy Mayor.

Coun Moulton said Coun Miller would bring and "incredible energy" to the job and would be an "excellent" first citizen of the borough.

Coun Miller named her two chosen charities for the mayoral year as Home Start - a charity based in Colliers Wood who help families in need - and the children's Polka Theatre in Wimbledon.

A unanimous vote of thanks was given to the outgoing mayor, Coun David Williams, and deputy mayor Coun John Bowcott.

Leader of Merton council, Councillor Stephen Alambritis, said Coun Williams's dedication, professionalism and skill in charing meetings had resulted in a very successful mayoral year in Merton, and in raising more than £50,000 for his charities.

Speaking about the new group she plans to form, Coun Evans said: "There will be no secret backroom deals and no whip; we’ll each act individually according to our conscience and in the best interests of the borough."

Coun Evans told the Wimbledon Guardian: "What the future holds for me now I have no idea, but that’s not what this is about.

"It’s about being able to hold my head up high and walk away because there are lines I will not cross."

She added: "I don’t believe over 2,200 people voted for me in Hillside because they wanted a representative who would condone treacherous and unethical behaviour among her colleagues, so I trust they’ll understand.

"I’ve worked very hard for them for the last three years and will continue to do so, until 2014 at least."