Hellsborn's party colleagues have however condemned his argument.
"If there hadn't been any Islamisation or mass immigration then there wouldn't have been anything to trigger Behring Breivik to do what he did," wrote Hellsborn, who represents the party in Varberg in western Sweden.
"The ultimate responsibility is with the perpetrator, but if you are to discuss the underlying reasons which motivated him then it was caused by multiculturalism," Hellsborn explained to the local Hallands Nyheter daily.
Hellsborn furthermore writes that he feels no shame or guilt that he and Anders Behring Breivik share the same nationalist ideology. Those who should feel guilt are those he calls "cosmopolitans" and argues that "in a Norwegian Norway this tragedy would never have happened".
The political agenda detailed in Anders Behring Breivik's "manifesto" bears striking similarity to the ideology professed by the Sweden Democrats and when asked if the the party should shoulder some responsibility, Hellsborn replied:
"No, Breivik is a product of the multicultural society. If Europe had not become multicultural then the shootings would not have happened," he told Hallands Nyheter.
Sweden Democrats party secretary Björn Söder on Tuesday distanced the party from the Hellsborn's comments.
"The party does not stand behind the analysis. One should be very careful conducting an analysis at this early stage. And that is something we have communicated to Hellsborn," Söder told news agency TT.
"Of course no one other than the perpetrator has responsibility for what has occurred," he said.
The party and its rhetoric has had to shoulder the blame in some quarters of the public debate for contributing to the ideological climate which allowed Behring Breivik's hatred for society turn into violent acts.
While also recognising that it is Behring Breivik who his responsible for his actions and noting that most of the mainstream anti-Muslim movement discounts violence as a legitimate working method, the anti-racist magazine Expo, is one of the groups who share this view.
"It is impossible to disregard the ideological environment where Behring Breivik has structured his views on society if you want to understand the causes behind the terrorist attack in Oslo the 22 of July," Expo wrote in a statement on Monday.
"This ideological environment is built up around blogs, websites, networks and ideologues. It reaches into the various european populist right winged parties."
Björn Söder rejected the assertion that Behring Breivik's terror manifesto echoed the ideas of the Sweden Democrats, its view on Islam for example, which party leader Jimmie Åkesson has identified as "Sweden's greatest foreign threat".
"It's a big mishmash of lots of things that will justify what he has done. It is especially the contempt of democracy and a fetish for violence that pervades the entire manifesto," Söder said.
"But of course there is criticism of immigration, but there is also freemason mysticism and conservatism and liberalism. You try to pick parts out of context and attack us, and I think this is just as wrong as when Hellsborn says that multiculturalism has created Breivik," he said.
Sweden Democrat MP Kent Ekeroth also courted controversy on the evening of the attacks when used his twitter to ask: "Anyone care to guess who is behind the bombs in Norway?.
He was warned by party secretary Björn Söder not to speculate before the cause of the attacks was known, but proceeded to write: "No I am not going to call you Islamophobes".
Press secretary to Jimmie Åkesson, Linus Bylund, was also quick to draw conclusions, tweeting: "The next bastard who gushes about how sad it is for the nice Muslims when bleeding Norwegians are all over the streets will be blocked".