Christer Winbäck, the Liberal Party foreign affairs spokesperson, says Sweden's credibility as a country opposed to nuclear weapons could be at risk.
"I'm surprised. We have been clear in the past that the reason why we want countries to completely stop using nuclear weapons in the future is because of the impact such weapons have on humanity," Winbäck tells Swedish Radio.
However, Carl Bildt hit back when he rang in to a listener call-in show on Swedish Radio, saying the UN declaration against nuclear weapons was like taking a side track in the conversation that other serious countries stay away from.
He says Sweden is doing a lot of work to reduce nuclear weapons. "We are pursuing very serious work concerning nuclear disarmament, mainly on issues of test ban treaties, to get countries to sign them. Tactical nuclear weapons, we are working with other countries on this issue. The Iran question which is probably the most serious right now."