"I think it's unfortunate," Reinfeldt told TT news agency when asked about the initiative Cameron announced on Monday.
"I believe in a Europe that should be open, where we have free movement, and where we instead ask ourselves how people who come here can get work more easily," he said.
Speaking to Sveriges Radio (SR), Reinfeldt also pointed out that Sweden, when it opened its borders to greater immigration from Bulgaria and Romania, saw no major influx of people seeking to abuse the country's generous welfare system and benefits.
"We didn't see this big social tourism that everyone warned us about, and it might be wise to share that experience with others," Reinfeldt said.
Reinfeldt's criticism of Cameron was echoed by Christian Democrat party leader and Social Affairs Minister Göran Hägglund.
"I think it's a terrible way to express oneself. I think his speech is very, very, unfortunate," Hägglund told SR.
Specifically, Hägglund took issue with how Cameron "pitted us against them" when speaking of migrants.
Cameron on Monday proposed to limit newcomers' rights to housing, unemployment and health benefits, saying those services were "something earned, not an automatic right."
Immigration has shot up on the political agenda as the UK responds to the European Union lifting work restrictions on Bulgarians and Romanians in 2014.