Hong Kong's former chief executive Donald Tsang has been sentenced to 20 months in jail in the highest-profile corruption case the semi-autonomous Chinese city has ever seen.

Key points: Judge Chan calls conviction biggest fall from grace he has ever seen

Judge Chan calls conviction biggest fall from grace he has ever seen Donald Tsang faces a retrial later this year for a bribery charge linked to the same case

Donald Tsang faces a retrial later this year for a bribery charge linked to the same case Hong Kong's judicial independence from China has been under pressure due to a string of recent high profile cases

The 72-year-old was at the helm of Hong Kong's administration from 2005 to 2012, and was found guilty of misconduct over a conflict of interest involving a property deal and the granting of broadcast licences.

The case centred around the purchase of a luxury property in the neighbouring city Shenzhen that Tsang was negotiating to buy from a Hong Kong tycoon.

A jury last week found Tsang had failed to disclose the deal when he approved three radio broadcast licenses for a company the tycoon, Bill Wong Cho-bao, held a 20-per-cent stake in.

In delivering the 20-month sentence, the judge said "never have I seen a man fall from so high".

After the sentence, Mr Tsang's wife Selina Tsang vowed the couple would "toughen up and face it," local media reported.

Donald Tsang faces a retrial later this year for a bribery charge linked to the same case.

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"Despite him being a rather unpopular leader at the end of his tenure, Hong Kong people don't show any strong emotions about the case", Joseph Cheng, a retired political professor, said.

"Hong Kong people are very happy that no-one is beyond the reach of the law, and that the independence of the judiciary has been upheld," he said.

The case comes just days after seven police officers were handed two-year jail sentences for assaulting a protestor during the 2014 pro-democracy demonstrations in the city.

It attracted huge attention, including a campaign by pro-Beijing groups to condemn the judge.

The city's judicial independence, enshrined under a 50-year "one country, two systems" policy that Beijing granted upon Hong Kong's return from British control to China in 1997, has been under pressure due to recent high profile cases.

Five Hong Kong-based booksellers were detained by mainland authorities in 2015, including at least one who was believed to have been taken by mainland agents operating secretly in Hong Kong.

More recently, Chinese billionaire Xiao Jianhua was taken across the mainland border from a Hong Kong hotel by a group of men, in a murky case that Hong Kong police are investigating.