A professor at one of China's most prestigious universities has stirred up a hornets' nest in Hong Kong after publicly calling residents of the territory "bastards", "thieves" and "dogs of British imperialists".

Kong Qingdong of Peking University launched the tirade during a webcast interview at the weekend that has tarnished the reputation of his employer and intensified an already fierce debate about relations between Hong Kong and the mainland.

Recent surveys suggest only a third of the 7 million people in the territory consider themselves Chinese though almost 15 years have passed since the handover from British rule.

The differences have been apparent in a series of seemingly trivial disputes that have sparked protests or gone viral on the internet.

The Italian luxury goods retailer Dolce and Gabbana was forced to apologise last week after security guards at one of its Hong Kong shops blocked locals who tried to take photographs, yet allowed mainlanders and foreigners to snap freely. This perceived discrimination in favour of wealthy mainland tourists prompted a protest by about 1,000 people.

It was followed soon after by a mobile phone video of Hong Kong commuters criticising mainlanders for eating and leaving crumbs on the subway. This case prompted a fierce online debate between those who accused mainland visitors of lacking manners and abusing their maternity system on one hand, and, on the other, those who attacked the snobbish attitude of Hong Kongers and exploitation of mainlanders as factory fodder.

For Kong – an ultra-nationalist who claims to be a descendant of the sage Confucius – such cases are unforgivable.

"To the best of my knowledge, many people in Hong Kong don't consider themselves to be Chinese. Those types of people are used to being the dogs of British imperialists – they are dogs, not humans," the professor of Chinese studies told the host of the news website v1.cn.

He went on to accuse Hong Kong tour guides of cheating visitors and to insist that all Chinese people should speak Mandarin rather than local dialects such as Cantonese. The video has since circulated widely on the internet.

Coming from a professor at a university that educates many of China's top officials, these vitriolic comment stirred up a passionate response. On Sunday, several hundred demonstrators – many with their dogs – gathered outside the China Liaison Office in Hong Kong to express their anger. Some chanted that it was better to be a dog in Hong Kong than a human on the mainland, according to local media reports.

Peking University has yet to comment on the case. Kong, however, has since tried to distance himself from his comments by saying they have been taken out of context – though the video was apparently uncut and his vitriol unrelenting.

In a blogpost on Monday, Kong denied insulting all Hong Kongers.

"I know there are many nice people in Hong Kong, but many Hong Kong people are still dogs" he wrote.

It is not the first time that Kong has provoked controversy. He participated in the "Confucian peace prize" – set up as a rival to the Nobel – which gave its latest award to Vladimir Putin.

He has also denied North Korea had ever faced famine and said he would not be sad if journalists were lined up and shot.