Sikorski said on 6 January that the project, favoured by Russia and Germany, has been pushed through despite Poland's disapproval and does not make economic sense.
The Polish authorities have pointed out several times that the Russo-German consortium led by Russian giant Gazprom has not been able to explain why a sea route is better than the cheaper land option.
Sikorski has long been a vocal opponent of the pipeline. He caused a stir in 2006 when, as defence minister, he said the Nord Stream project echoed the 1939 Molotov-Ribbentrop Pact, under which Nazi Germany and the Stalinist Soviet Union carved up Poland at the start of World War II.
Poland and other ex-communist Baltic Sea states such as Estonia and Lithuania have warned that the pipeline will increase Europe's direct dependence on Russia for natural gas (EurActiv 27/08/09).
Nord Stream, along with its South Stream counterpart, is part of a Russian effort to diversify regional transit via routes that avoid politically-sensitive territory in Ukraine (see EurActiv LinksDossier).
Denmark granted a construction permit for the Nord Stream pipe last October (EurActiv 22/10/09).
Russian and German authorities also delivered at the end of December permits for the construction of two sections of Nord Stream in their waters, a 123km section and a 50km section respectively.
Finland is the only participating country that is yet to grant a permit. Nord Stream, for its part, is confident that the construction of the pipeline will go ahead as planned.
"We are firmly on schedule to start construction of the pipeline in spring 2010 and to start transporting gas in 2011," Nord Stream Managing Director Matthias Warnig said in a statement on the project's website.