The German Ambassador to the UK has said there is “no need to apologise” for security breaches which led to a call between top army officials being leaked by Russian sources.
Miguel Berger told the BBC’s Today programme one of the participants had likely dialled in via an insecure line.
This made it possible for Russia to intercept the call, he said.
In the audio, officials can be heard discussing details of alleged British operations on the ground in Ukraine.
Mr Berger hit back at criticism by former UK Defence Secretary Ben Wallace, who said Germany was “pretty penetrated by Russian intelligence” and “neither secure nor reliable”.
“It is extremely unhelpful what Ben Wallace has done,” Mr Berger said.
“This is what Russia wants.”
The publication of the call was a Russian “hybrid attack”, he added.
Mr Berger also said German Defence Minister Boris Pistorius had called allies to explain Germany’s position over the leak.
He said preliminary results of an investigation by military intelligence showed that the leak was down to “an individual mistake by one of the officers”.
The call had been intercepted because one of the participants had connected in an insecure way, he said.
“I think that is a good lesson for everybody: never use hotel internet if you want to do a secure call,” Mr Berger advised listeners of the Today programme.
In the leaked recording, four senior German military officers are seemingly heard discussing the prospect of Ukraine using German-made Taurus cruise missiles to hit the Kerch Bridge, which links Russia to the Crimean peninsula, illegally annexed from Ukraine in 2014.
German Chancellor Olaf Scholz has repeatedly ruled out sending the Taurus missiles to Ukraine.
Mr Berger said Mr Scholz was being careful about how to increase support to Ukraine, so as not to lead to escalation which could lead to “consequences we all don’t want to see”.
If Germany were to provide Taurus to Ukraine there would be “potential for escalation”, he said.
The missiles have a range of around 500km (300 miles) – enough to potentially hit Russian territory.
Ambassador Berger said allies’ focus needed to instead on how to supply enough ammunition to Ukraine.
Kyiv has said it is losing ground to Russian forces in part because of diminishing ammunition supplies.