Bosch has hit back at Dyson for allegations that its vacuum cleaners cheated in energy efficiency tests.
The allegations led to comparisons with the Volkswagen emissions scandal and the claim that Bosch was the "Volkswagen of vacuum cleaners".
The manufacturer of British vacuum cleaners launched legal action last week against Bosch, which strongly rejected the claims.
Karsten Ottenberg, chief executive of Bosch's home appliances unit, said: “We have long since been aware that James Dyson has a history of taking a very aggressive approach against his competitors.”
"With his completely unfounded accusations of cheating in the past week he has now overstepped the mark, which is why we will now initiate legal steps against Dyson," Mr Ottenberg said.
Sir James Dyson said in a statement that Dyson would not be diverted from what it called a "crucial consumer issue".
"What Bosch and Siemens have done we believe circumvents the purpose of the EU energy regulations and misleads consumers," he said.
The latest claims open another chapter in the long-running feud between the two firms.
In 2012, Dyson sued Bosch for allegedly planting a mole in its engineering team at its Wiltshire headquarters.
It claimed the 'spy' worked on its digital motors, which are used in its cordless technology and Airblade hand dryers.
Bosch has said it can prove that Dyson had advertised incorrect values on the energy label for its appliances.
