Clinton and Obama row over backer

It was sparked after Hollywood mogul David Geffen hosted a fundraiser for Mrs Clinton's rival and called her overly ambitious in an interview.

Mr Geffen, who once backed Bill Clinton, also claimed the former first lady might be a "polarising" figure.

However, Mr Obama's camp has refused calls to denounce the remarks.

A spokesman for the Obama campaign noted that the former first couple did not complain when Mr Geffen raised millions of dollars for Mr Clinton's presidential campaign and was entertained at the White House.

'Positive campaign'

Ms Clinton's camp have questioned Mr Obama's vow to stay away from "slash and burn" politics as a result of this latest row.

Asked about the row at a forum in the western state of Nevada, Ms Clinton said: "I want to run a very positive campaign, I sure don't want Democrats or supporters of Democrats to be engaging in the politics of personal destruction."

Mr Obama's spokesman, however, said that they did not wish to enter into a row between the Clintons and "someone who was once one of their biggest supporters".

The initial comments by Mr Geffen were first reported in the New York Times.

He said: "I don't think that another incredibly polarising figure, no matter how smart she is, and no matter how ambitious she is - and God knows, is there anybody more ambitious than Hillary Clinton? - can bring the country together."