The Stiftung Warentest a consumer watchdog suggested four of the stadia - in Berlin Leipzig Kaiserslautern and Gelsenkirchen - were 'substantially' unsafe while it deemed eight others 'clearly' unsafe.
The report claims the grounds fall short of the necessary standards in areas such as crowd safety.
Stadia in Gelsenkirchen and Leipzig for example were found by the group to have a lack of sufficient escape routes for spectators. The report says stairs were too steep and that there were obstructions preventing a quick exit.
Beckenbauer however hit back at the findings and insisted the grounds are in good condition to host the tournament which begins on June 9.
'I'm sick of all this 'we know best'' he told the Bild newspaper.
'Stiftung Warentest may know a lot about facial cream olive oil and vacuum cleaners and that is what they should stick to.'
Representatives of some of the venues highlighted also hit back.
'I don't see this as a very serious study' said Hans Rutten business manager of Kolner Sportstatten GmbH which is responsible for the WM-Stadion Cologne.
'We don't see any reason to start any extra building work.'
Berlin which will host the final on July 9 was also criticised for having insufficient escape routes in the event of an emergency but the representative of the Olympiastadion Berlin GmbH Christoph Meyer believes the recent work done on the stadium is satisfactory.
'We will obviously look at the results but in Berlin we have a building which has lasted the test of time and was renovated between 2000 and 2004 according to regulations for buildings of historical significance' he said.
Leipzig Zentralstadion Betreibergesellschaft mbH business manager Winfried Lonzen doubted the credibility of the report into the east German stadium which has already been given a safety licence.
'At the end of 2004 the Zentralstadion passed all tests (for insurance building regulations and fire protection) with no problems' he said.
'Even FIFA saw no problems with the stadium when Germany played Cameroon and during the Confederations Cup.'