Bernie Sanders says he will continue to fight against Hillary Clinton until the last primary

Mr Sanders’ campaign said he will compete in Washington DC on 14 June

Mr Sanders' senior adviser said 'every voter' should have the chance to vote for the senator

Bernie Sanders has said he will compete for the position of Democratic nominee until the very last primary in Washington DC.

On the same evening that the Vermont senator looks set to lose New Jersey to Hillary Clinton and hours before the results are in for the vote in California, Mr Sanders sent out a campaign email to supporters which encouraged them to vote and to volunteer in anticipation of the final democratic primary in Washington DC on 14 June.

The email has sent a signal that Mr Sanders is determined to continue to fight against Ms Clinton to the very last vote.

A senior adviser to Mr Sanders, Tad Devine, told the Associated Press that the senator will campaign ahead of 14 June, which is “very important” and that Mr Sanders intends “to let every voter cast their vote”.

The adviser was asked if Mr Sanders' strategy to convince superdelegates to support him hinges on winning the Golden State, and Mr Devine replied that the campaign will “have to have a very compelling argument with them.”

Mr Sanders and his supporters were quick to call out the Associated Press, CNN and other media outlets for claiming the race was “over” before the convention.

He said he was “upset” and “disappointed” that the calls were made the evening before the country’s “largest primary” on the West Coast.

Mr Sanders' campaign has continued to encourage voters to go to the polls and is still strongly channeling Mr Sanders' message over social media, the same platform which enabled the candidate to fundraise around $200 million via small donations.

Ms Clinton has a clear lead on superdelegates, otherwise known as party insiders, which, combined with the number of pledged delegates from state primaries and caucuses, pushes her towards securing the nomination.

Superdelegates can change their minds and switch allegiance at the democratic convention, therefore the nominee cannot be officially announced until late July.

Mr Sanders was asked this week by a female reporter whether he is "sexist" as his refusal to quit the race is presenting a hurdle to electing the first female president.

"Is that a serious question?" replied Mr Sanders.

“I don’t think it is sexist,“ he said. "Our focus right now is running and winning right here in California and the second point that I have made is that it is absolutely imperative that we defeat Donald Trump as a candidate for president of the United States. I believe that I am the stronger candidate.”