The Democratic convention – an event intended to forge party unity – got off to a chaotic and toxic start after a senior official was heckled by supporters of Bernie Sanders who accuse her of plotting against their candidate.

Debbie Wasserman Schultz, who announced on Sunday night that she is to stand down head of head of the Democratic National Committee (DNC) was repeatedly booed and mocked by supporters of Mr Sanders as she tried to speak on Monday morning.

“We have to make sure that we move forward together in a unified way,” Ms Wasserman Schultz said.

Bernie Sanders officially endorsed Ms Clinton this week (Reuters)

“We know that the voices in this room that are standing up and being disruptive, we know that is not the Florida that we know. The Florida that we know is going to make sure that we continue to make jobs.”

But according to the Associated Press her efforts to address the gathering was hampered by supporters of Mr Sanders waving placards and shouting “Bernie, Bernie”.

The furore centers around allegations, raised for more than six months, that Ms Wasserman Schultz and her staff at the DNC were biased in favour of Ms Clinton. They said that the schedules of debates, fund-raising and access to a supporter database were proof that the DNC was tying to help the establishment candidate defeat the insurgent Vermont senator.

On Friday, supporters of Mr Sanders received what they said was proof of their suspicions when leaked emails revealed that members of the DNC had been plotting against Mr Sanders. One exchange showed that they planned to try and expose him as an atheist.

An email from May 2016 and sent from DNC chief financial officer Brad Marshall suggested that they should “get someone to ask” Mr Sanders his views on religion.

“It might make no difference, but for KY and WVA can we get someone to ask his belief. Does he believe in a God. He had skated on saying he has a Jewish heritage. I think I read he is an atheist,” wrote Mr Marshall. This could make several points difference with my peeps. My Southern Baptist peeps would draw a big difference between a Jew and an atheist.”

Mr Marshall has issued an apology and on Sunday, it was announced that Ms Wasserman Schultz was standing down as chairperson of the DNC after Mr Sanders had called for her to go.

Ms Clinton is relying on Mr Sanders bringing his energy to the campaign and the countless numbers of young people and progressives who came out to support him during the primary contest, vote for the former Secretary of State. On Sunday, Mr Sanders told ABC that he was not withdrawing his endorsement of Ms Clinton and said it was essential that people work to defeat Donald Trump.

“We have got to continue bringing people in, fighting for an agenda that works for working families and having the courage to take on the big-money people who today control our economic and political life,” he said.

On Sunday night, Mr Sanders welcomed Ms Wasserman Schultz’s decision to stand down. “While she deserves thanks for her years of service, the party now needs new leadership that will open the doors of the party and welcome in working people and young people,” he added. “The party leadership must also always remain impartial in the presidential nominating process, something which did not occur in the 2016 race.”

On Monday, Robby Mook, campaign manager for Ms Clinton, said that he was not concerned about the jeering or booing of Ms Wasserman Schultz.