Staff at the UK embassy in the Eastern European's capital, Minsk, unveiled a rainbow flag last Thursday to mark International Day Against Homophobia - an annual initiative started ten years ago.
In a statement, the country's Interior Ministry accused the UK of creating "problems where they do not exist", adding that the Day has never been widely celebrated in Belarus.
It continued: "The reason for this is obvious - the overwhelming majority of Belarusians stick to traditional family values, including Christian ones. And such statements are a challenge to these values."
The document went on to say heterosexual relationships were the "only way to reproduction" and it described relationships between same-sex couples as "fake" and "the erosion of the truth".
Orthodox Christianity is the major religion in Belarus, but there are also significant Roman Catholic, Protestant and Jewish communities. Homosexuality is not illegal but it is considered taboo.
Belarus, which has been governed tightly by President Alexander Lukashenko since 1994, has been described as the last dictatorship in Europe.
In a video released by the UK embassy in Belarus last Thursday, the British Ambassador to Minsk warned that the lesbian, gay, bisexual and transgender community "suffers greatly" in certain parts of the world.
Потому что каждый человек должен иметь возможность жить без дискриминации и преследования. Новый выпуск видео-блога Посла Фионны Гибб о #IDAHOBIT2018 ️ pic.twitter.com/QdkdSDodcl
— UK in Belarus (@UKinBelarus) May 17, 2018
Ms Fiona Gibb added: "Yet, even in the countries where there is progressive legislation in place, social norms may lag behind.
"Here in Belarus, we seek opportunity to promote human rights and prevent discrimination."
British Embassy Minsk told Premier it would not be commenting on the Belarussian authorities' response to the flag.
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