HONG KONG - Sixteen years after Hong Kong returned to Chinese rule, public discontent with Beijing is swelling and protesters have been rallying around an unexpected symbol - the British colonial flag.

Tens of thousands have taken to the streets in recent months in marches against Chief Executive Leung Chun-ying, who took over from Donald Tsang last July after being elected by a 1,200-strong pro-Beijing committee.

On several occasions the old blue flag, which incorporates the Union Flag, has been flown by protesters on the streets of what is becoming an increasingly divided Hong Kong, both embarrassing and infuriating Beijing.

While Leung's supporters say he is tackling pressing social issues such as affordable housing and the strain on public services, his critics see him as a stooge for Beijing and are angry over a widening poverty gap.

In September, he backed down from a plan to introduce Chinese patriotism classes in schools, which had incited mass protests and was viewed as an attempt to brainwash children into accepting doctrines taught on the mainland.

The founder of a group mobilising Hong Kongers to fly colonial flags said it did so because the city was worse off after 16 years of "encroachment" by Beijing, stressing it was not because of any desire to see Britain rule again.

"Our freedom and everything else has gone downhill since (the handover)" said 26-year-old Danny Chan from the "We're Hong Kongese, not Chinese" Facebook group, which has been "liked" by nearly 30,000 people.

Hong Kong's semi-autonomous status enshrines civil liberties not seen on the mainland, including the right to protest, until 2047 under the "One country, two systems" handover agreement.