Addressing crowds at the Baltic resort of Usedom, Mr Kohl said the PDS successor party to the East German Communists had learnt nothing from history and even today denied crimes committed in the name of its ideology.
He then turned on his real target: the opposition Social Democrats (SPD), who represent the main challenge to his continued rule and who, in the east German state of Saxony-Anhalt, have recently formed a minority government with the Greens which can only survive with the support of the local PDS.
'It is a disgrace for Germany that the SPD, out of pure lust for power, has joined forces with such people (the PDS),' he declared. 'We have to hold on to the gift of German unification with both hands.'
The SPD's apparent arrangement - or at least tacit understanding - with the PDS in Saxony-Anhalt has given Mr Kohl's Christian Democrats (CDU) a golden opportunity to seize the political initiative.
'Onwards to the future - but not in red socks]' declares the slogan on a newly- produced CDU poster depicting a washing-line and a red sock, a colloquial term for an old Communist. The CDU's more conservative Christian Social Union (CSU) allies in Bavaria have gone even further. Their summer poster features the bearded face of Karl Marx with the words: 'I'm back] Thanks to the Social Democrats'.
Back at SPD headquarters, the party, perhaps sensing that it has shot itself in the foot, is on the defensive. 'This is not a model for Bonn,' the SPD's party manager, Gunter Verheugen, stresses, referring to the Saxony-Anhalt government.
'We have nothing in common with the PDS. This party is not a partner for us. There will be no coalition with them or government tolerated by them.'
SPD leaders have also been sniffing around the archives, digging up a few pictures of Mr Kohl in animated conversation with Erich Honecker during the former East German leader's visit to Bonn in 1987. 'Now we are out of our socks, Mr Kohl,' reads the caption, a colloquialism meaning, 'now we are astonished'.
It is still too early to predict what impact the trading of such insults will have. According to most opinion polls, Mr Kohl has already surged into a comfortable lead.Reuse content