Organised by the left-wing Radical Independence Campaign (RIC) which includes the Scottish Greens and Scottish Socialists, it claims Britain is "for the rich", and focuses relentlessly on the UK's chronic social and economic problems.
It describes Britain as a place with high infant mortality, poverty pay, staggering inequality between rich and poor, and "the least happy children in the developed world". Its conclusion to voters is: "Scotland doesn't have to be like this. Vote Yes."
The Tories said it was a campaign based on "hatred", while Labour called it "appalling".
The SNP last night stressed Radical Independence was "organisationally separate" from the party and the official Yes Scotland campaign.
Thousands of flyers and posters declaring "Britain is for the rich, Scotland can be ours" will now be distributed around social housing schemes as part of a drive to target the estimated two million people in Scotland who don't vote.
RIC organisers, who see the referendum as a class conflict in which the rich are voting No to avoid radical change, say they want to attract people who feel conventional politics is irrelevant to their lives, and who therefore "have nothing to lose" by voting Yes.
Around half of the Scottish electorate choose not to vote in elections, a huge reservoir of potential support in the referendum if roused.
To help target these people, the RIC plans mass canvas operations in poorer areas to encourage people to register to vote. The first such drive will be on Wednesday evening in Easterhouse in Glasgow.
RIC has previously been supported by a range of SNP figures, including MSP Christina McKelvie, who spoke at its conference last year, Treasury spokesman Stewart Hosie MP and Holyrood chief whip Joe Fitzpatrick, who both campaigned alongside RIC Dundee earlier this month.
Dennis Canavan, the chair of Yes Scotland, has also spoken at the last two RIC conferences, as have two of his fellow Yes Scotland board members - Colin Fox, leader of the Scottish Socialists, and Green MSP Patrick Harvie.
The SNP's attack on Coalition welfare reforms and its promise to end the so-called bedroom tax are aimed at the same unemployed and low-paid workers targeted by RIC.
But the RIC's hardline anti-British theme will trouble the SNP leadership as the party wants to avoid criticism for negative campaigning.
RIC members, frustrated by the SNP's cautious approach, say the time for holding back is over, and that voters should be told Britain is a deeply dysfunctional and unfair society.
One RIC organiser told the Sunday Herald: "It was fine for the SNP to decide not to attack Britain too much, but someone had to do it."
RIC members also believe Chancellor George Osborne's flat rejection of a currency union with an independent Scotland - denounced by Alex Salmond as "bullying" - gives the Yes camp an opportunity to take a more aggressive stand.
RIC organiser Jonathon Shafi said he was already finding three-to-one support for a Yes in the communities "professional" politics had ignored.
He said: "Change is in the air. We are on the verge of a wider awakening.
"Corporate Britain is sewn up for the rich. Most people know they are the butt of Tory Britain's 'we're all in it together' joke.
"It will not take much to galvanise that frustration into a clear understanding of just how bad Britain has been."
Shadow Scottish secretary Margaret Curran, whose Glasgow East constituency includes Easterhouse, said: "I know people in Easterhouse are too wise to be won over by this scaremongering from the anti-UK campaign. These are appalling tactics.
"The SNP and the Yes campaign need to come clean on their involvement with this campaign and whether they signed off these tactics."
Conservative deputy leader Jackson Carlaw added: "This makes Alex Salmond's 'positive vision' look very foolish indeed.
"These individuals are campaigning on a theme of hatred.
"They are basically everything the Yes camp said it would never become, but senior SNP officials are canvassing with them hand in hand."
There are some question marks over the accuracy of the RIC campaign.
Its claim that Britain has "the worst infant mortality rates in Europe" is despite mortality rates in Bulgaria and Romania being more than double those in the UK.
The RIC campaign taps into a significant but under-reported aspect of the referendum: class. Support for a Yes is greatest in deprived areas, while affluent areas back a No.
In December, Ipsos Mori's Scottish Public Opinion Monitor reported 47% support for independence in the most deprived 20% of communities, ahead of 45% support for the Union.
In sharp contrast, the most affluent 20% of neighbourhoods were 68% for Yes and 26% No.
According to the 2011 Scottish Census, around 19% of households are headed by a person in social grade AB, which refers to higher-level professionals and managers.
Around 32% are headed by C1 junior clerical and professional workers, 22% are headed by C2 skilled manual workers, and 28% of household heads are DE semi-skilled or unskilled manual workers and the unemployed.
It is the DE group which RIC is focused on.
Last month, a TNS poll found support for a Yes vote was highest among the DE group, and lowest among the ABs, but also that the DEs had the highest numbers of non-voters.
A Better Together spokesman said: "Clearly any pretence of a positive campaign has been abandoned by the Nationalists.
"How does this square with Alex Salmond's assertions that those seeking to break up the UK offer only hope and positivity?
"There is a strong positive case for Scotland remaining in the UK. Ours is a campaign founded on an idea much bigger than the nationalist vision of division and grievance."
An SNP spokeswoman said: "This does not reflect our positive approach to the referendum. RIC is one of many different groups campaigning for independence, and is organisationally separate from both the SNP and Yes campaign."