"Current policy of the UK government towards Russia is a very dangerous game played with the British public opinion, which not only sends the investigation upon an unhelpful political track but also bears the risk of more serious long-term consequences for our relations," the mission's press secretary said in a statement.
The comments came amid speculation that British Prime Minister Theresa May could publicly blame Moscow for the nerve agent attack earlier this month on Russian double agent Sergei Skripal and his daughter Yulia.
Britain's probe into the March 4 attack in the south-western English city of Salisbury "is being concluded in a non-transparent manner", the embassy statement said.
It said that from the first reports of the poisoning, the embassy had requested from Britain's foreign ministry information about Skripal and his daughter, and the investigation.
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"British officials don't provide any additional information and don't distance themselves from the media campaign," it said.
It added: "We would like to stress once again that we are outraged by the anti-Russian media campaign, condoned by the government, that influences the investigation and has a psychological effect on British residents.
"UK-based Russian journalists are receiving threats," it said, without elaborating.