Vile cartoons of Muslims swilling alcopops and chasing pre-pubescent girls, as well as graphic depictions of Lee Rigby's murderer, could be broadcast on the BBC and ITV this week, submitted as the BNP's official party election broadcast.
The party can submit a five-minute broadcast to major channels ahead of the May European elections.
An 10-second clip, leaked to The Huffington Post UK, shows an animation of a girl and the BNP's bulldog mascot looking at a billboard which says 'Muslim Grooming Gangs At Large'.
She is then confronted with a gang of Muslims in traditional dress, swigging blue WKDs, as a background song to the tune of 'All Things Bright And Beautiful' mentions how "there's some who prey on little girls from takeaways and taxis".
The girl walks past a burqa-wearing Big Issue seller with a small boy, with a sign saying 'Sale' around his neck.
She encounters a black silhouette, with blood red hands, a clear reference to Woolwich soldier Lee Rigby's murderer Michael Adebolajo, as the song references those who "kill with knives and axes".
The BNP has party election broadcasts scheduled ahead of May's European Parliament elections. The five-minute broadcast will go out on prime-time BBC and ITV on Tuesday.
Simon Darby, the BNP's press officer, said the description of the clip matched that the party had submitted to broadcasters, though he said he was angry the video had been leaked ahead of time.
"I haven't had any indication it isn't going to be broadcast, as is," he said. "It's going to get an enormous audience, at peak time. Usually they try and put it in the middle of the night."
The party has been teasing images of its cartoons on its website, counting down the days until the broadcast. The cartoons on the website match the style of cartoon in the clip seen by HuffPost UK.
The BNP website told members: "We’re counting down the days till it’s here… and believe the hype – it’s well worth the wait!"
Nick Lowles, of anti-fascist group Hope Not Hate, told HuffPost UK he would be astonished if the clip were broadcast in its current form. "It is inconceivable this could be broadcast, especially since the BBC have rejected less extreme broadcasts in the past," he said.
"This is a desperate attempt at publicity by a party with no profile and no platform," he said, calling the clip "clearly the most provocative thing they have ever done".
Channel 5 banned a broadcast by the BNP in 2004 after it was set to feature the mother of a teenage girl who claimed her daughter was drugged and gang-raped by Asian men in Keighley. In 2007, the BBC's lawyers insisted changes be made before a BNP party political broadcast went out, but did not discuss details as to why.
Three years later, prior to the General Election, Unite Against Fascism demonstrated outside the BBC as the party's broadcast was aired.
Lowles said BNP members had been discussing the broadcast for several weeks on social media, and mentioned it was possible that officials knew it would possibly be rejected, and had planned to make it a free speech issue.
The BBC told The Huffington Post UK that a BNP broadcast would be shown on BBC2 at 17.55 on Tuesday, but would not confirm the content.
"The content of party election broadcasts is a matter for the political parties," a spokeswoman said. "However, it is then the broadcasters’ responsibility to make sure it is compliant with relevant broadcasting regulations and the law."
The corporation's guidelines state that parties must "ensure broadcasts abide by rules laid down by the BBC and Ofcom... [which] include an obligation to observe the law, for example on libel, copyright and incitement to racial hatred and violence."
The party has until Monday morning to submit a final version, the BBC's guidelines state.
A broadcast is scheduled for 18.25 on ITV, but the corporation did not return requests for comment.
The BNP are not on the list of major parties. But Ofcom rules state that broadcasters should set a criteria so that other registered parties can qualify for a broadcast, and in 2014 that includes all parties that are running full lists of candidates in all English electoral regions, a spokesman for the watchdog said. The BBC has its own in-house guidelines.
This article has been amended to reflect updated rules from Ofcom