Today, BSH Group says it "strenuously rejects" the company's claims. "We have long since been aware that James Dyson has a history of taking a very aggressive approach against his competitors and has a desire to be in the public eye," Ottenberg says. "With his completely unfounded accusations of cheating in the past week he has now overstepped the mark." Going further, the company says it's cleaners are tested rigorously and in line with the requirements set out by the EU Energy Label and Ecodesign Directive.

The crux of the argument comes down to a set of sensors inside Bosch and Siemens' vacuum cleaners. In short, they recognise how much dirt is in the dust bag and adjust the motor appropriately, ensuring there's no loss of suction. This, Bosch argues, improves performance and cuts down on overall cleaning times. However, the company doesn't reject Dyson's point about the fluctuating power consumption -- it simply defends the technology and says it's following EU test protocols to the letter. Dyson's true issue, it seems, is with the testing procedures -- the company has already triggered a judicial review with the European Court, and a decision is expected before the end of the year.

In the meantime, we'll have to put up with some more mud-slinging between Bosch and Dyson. It's now the former's turn to take a quick jab -- today, it's reminding customers that Dyson was caught selling vacuum cleaners with misleading energy labels last year.

Update: Dyson says it's "disappointed" with the action taken by Bosch, and believes this is an issue about consumer trust, not a simple falling out between competiors. In a statement, the company says the legal action is a move to "try and divert attention away form the very serious alllegations faced by the company."

James Dyson added: "We will not be diverted from what is a crucial consumer issue. What Bosch and Siemens have done we believe circumvents the purpose of the EU energy regulations and misleads consumers."

So there you have it. Neither side is backing down, at least for now.

[Image Credit: Bloomberg via Getty Images]