Alexander Gauland, 76, a top candidate of the anti-immigration Alternative for Germany in September 24th elections, also said the country had sufficiently atoned for its crimes and should "reclaim its past".
The Social Democrats' Thomas Oppermann said such comments "expose Gauland as an ultra-right militarist", while Greens lawmaker Volker Beck labelled his statements "ever more disgusting".
As the latest controversy flared around the AfD, which campaigns under the slogan "Stop Islamisation", new polls suggested it would take 10 to 12 percent of the vote, giving it a good chance of becoming Germany's third strongest party.
Gauland has repeatedly sparked anger with provocative statements, saying no-one would "want as a neighbour" a German footballer with an African father, and recently saying a politician with Turkish roots should be "disposed of in Anatolia".
He made the comments on Germany's wartime and Holocaust past at a September 2nd party meeting, but footage of the speech only hit the public eye on Thursday.
In it, Gauland called for an end to German guilt over the Nazi era, saying that in Europe, "no other nation has so clearly dealt with its wrongful past as Germany".
"We have the right to reclaim not just our country, but also our past," he said.
"If the French are rightly proud of their emperor (Napoleon), and the British of (Admiral Horatio Lord) Nelson and (Prime Minister Winston) Churchill, then we have the right to be proud of the achievements of German soldiers in two world wars," he said.
Oppermann said his remarks showed the AfD was "clearly turning into a right-wing extremist party".
Pointing to WWII crimes such as "the cowardly mass murder of Jews", Beck of the Greens said: "There is nothing to be proud of".