In a Twitter thread on the subject of Anglo-Russian relations, the official Russian Foreign Ministry Twitter account cited what it said was anti-Russian statement made by the late British Prime Minister Margaret Thatcher. In 1991, Thatcher allegedly told an audience in Houston, Texas that it would be “economically feasible for only 15 million people to live in Russia.”
Some Russian journalists initially disputed that Margaret Thatcher gave any speeches in Houston during 1991. In fact, she delivered a speech in Houston that year to representatives of the oil industry, and the New York Times published an article about it. However, the speech was about environmental concerns and regulations and did not mention Russia.
The “quote” cited by the Russian Foreign Ministry actually comes from a Russian-language book by Andrey Parshev called "Why Russia is Not America."
Parshev claimed to have heard an audio recording of the speech, but has never provided any evidence for his claim. He has also several times changed the quote he allegedly “heard.” Most recently, he claimed Thatcher said that only 15 million people in the Soviet Union were employed in the most efficient sector of its economy.
Outside of Parshev’s book, there is no record of this alleged Thatcher quote or any of Parshev’s subsequent versions of it.