Hong Kong risks losing its autonomy due to increased intervention from the mainland and self-restraint imposed by the city's administration, Taiwan's Mainland Affairs Council has warned.

In a report released to coincide with the anniversary of Hong Kong's return to China, Taiwan's top mainland policy-making body said such developments contravened the 'one country, two systems' principle, under which the city would enjoy at least 50 years with a high degree of autonomy.

But the council was heartened by the fact that Hong Kong people insisted on promoting democracy.