Sweden is seeking to extradite Assange for the alleged sexual assaults of two women, which he denies. He spent nine days in custody in Britain after being detained on the assault charges before being released on bail in December.
Robertson said Reinfeldt's comments created a "toxic" atmosphere for his client in Sweden. He said the comments included claims Assange and Robertson made statements "condescending and damaging to Sweden" and implied that women's rights are unimportant.
"Mr. Assange is public enemy number one as a result of the prime minister's statement," Robertson said.
Clare Montgomery, an attorney representing Swedish authorities, dismissed the allegations.
"You might think those who seek to fan the flames of a media firestorm can't be surprised when they get burnt," Montgomery said.