SEOUL, South Korea — North Korea said on Saturday that a diplomat in its London embassy who recently defected to South Korea had fled rather than face punishment for various crimes, calling him “human scum.”

The statement, from the official Korean Central News Agency, was North Korea’s first reaction to the defection of Thae Yong-ho, its most senior official to defect in almost two decades. The defection of Mr. Thae, who was the No. 2 diplomat in the embassy, was announced by South Korea on Wednesday.

The North Korean statement said Mr. Thae, whom it did not identify by name, had been ordered in June to return from Britain to Pyongyang, the North’s capital, because he had embezzled state funds, sold official secrets and sexually assaulted a minor. The statement offered no evidence for those accusations.