A spokesman for the State Council Hong Kong and Macao Affairs Office said on Wednesday it was reasonable and lawful to disqualify Joshua Wong, whom he called a leader of a political group advocating "Hong Kong independence", from running in the upcoming District Council election.

An electoral officer in the Hong Kong Special Administrative Region ruled on Tuesday that Wong's nomination for the South Horizons West constituency of the Southern District Council was invalid. The District Council elections will be on Nov 24.

That ruling is based on sufficient facts and sound legal grounds, and it adheres to the "one country, two systems" principle and the Basic Law of the HKSAR, said Yang Guang, a spokesman for the Hong Kong and Macao Affairs Office.

"The decision upholds the rule of law and ensures the seriousness and fairness of the District Council election. We agree with, and support, this decision," he said.

Yang said Wong is one of the main people challenging the bottom-line "one country, two systems" principle and threatening the stability and development of Hong Kong.

He said Wong has been advocating "Hong Kong independence" and "self-determination", had openly claimed that Hong Kong is not part of China and has even begged for foreign interference in the recent unrest in Hong Kong.

"Wong is fundamentally inconsistent with the eligibility requirements for candidates to uphold the Basic Law and pledge allegiance to the HKSAR," Yang added.

Previous court judgments provide for the electoral officer to decide whether a candidate abides by the Basic Law based on public information, according to Ronny Tong Ka-wah, a barrister and member of the Executive Council, the chief executive's top political advisory body.

Wong and his party, Demosisto, hold that "Hong Kong independence" is acceptable if desired by a majority of local residents, Tong said, which is inconsistent with the Basic Law.

Tong added that he thinks the officer made the decision carefully with thorough consideration of previous court judgments. "It's reasonable for the electoral officer to find he (Wong) does not qualify under the Basic Law and other electoral laws."

Priscilla Leung Mei-fun, a Hong Kong barrister and lawmaker, said self-determination is inconsistent with the legal status of the Hong Kong Special Administrative Region as laid out in the "one country, two systems" principle - that the city is an inalienable part of China.

Neither the mainland nor the HKSAR has referendum laws, so advocating such is also inconsistent with the Basic Law, Leung said.

Lau Siu-kai, vice-president of the Chinese Association of Hong Kong and Macao Studies, said he was not surprised by the decision.

Given Wong's separatist inclinations and his close relationship with anti-China foreign politicians, it was difficult for the electoral officer to believe that he is loyal to the HKSAR and to China, Lau said.

He said that the SAR government has already taken a "very lenient approach" in verifying the qualification of candidates for the District Council elections, and Wong was the only person disqualified among over 1,000 candidates.