Leung denied he had been in touch with the returning officers on whether to allow independence advocates to join the race on September 4.

“The returning officers are performing their duties and using their powers in accordance with the relevant laws in Hong Kong. They are [doing so] in an impartial way without political interference,” Leung said, noting that some of those who were rejected were already seeking a judicial review, and there could be more legal challenges through election petitions after the polls.

When asked about the inconsistency and if the government had failed to draw a clear line as some independence advocates still managed to enter the race, Leung said it was entirely up to individual returning officers to determine who was eligible and who was not.

“This is not a decision made by a person in the government ... but the returning officer of the constituencies they are responsible for,” he said.

The political storm erupted last month when the Electoral Affairs Commission abruptly introduced a change to election rules requiring candidates to sign an additional declaration to reinforce their acceptance of Hong Kong’s status as an inalienable part of China.

It further escalated when returning officer Cora Ho Lai-sheung invalidated the candidacy of Edward Leung Tin-kei last week, even though the leader of the localist group Hong Kong Indigenous signed the extra form and agreed to drop his stance for independence in order to qualify.

The localist leader and university student stood a high chance of winning, having secured 16 per cent of votes in the New Territories East by-election in February.

The fallout took a worrying turn when Ho received a threatening letter with a razor blade enclosed over the weekend, while two suspects were arrested for allegedly making separate online threats against returning officers earlier in the week.

The election watchdog on Sunday expressed deep concern and regret over the alleged threats and intimidation, urging the public to deal with such disagreements through legal means.

Dr Chung Kim-wah, a political scientist at Polytechnic University, suggested Leung was only making a “technical denial” as it was hard to believe the city’s top official had no role to play in such critical decisions.

“Leung’s remarks would expose civil servants, whom the public are now pointing fingers at, to further exert pressure,” he said.

Outgoing Legco president Jasper Tsang Yok-sing on Sunday defended the ban as “necessary”, saying it was a move to stop activists from using the elections as a stage to promote their independence agenda.

The pro-establishment heavyweight also called on both the local and central governments to restore confidence in the “one country, two systems” principle, particularly among the city’s youth. “It would help suppress pro-independence ideas,” he added.

The Legco president, who has indicated his willingness to run for chief executive, was attending a public event at a time when such appearances by possible contenders are being seen as campaign-style efforts to win hearts and minds.

Financial Secretary John Tsang Chun-wah, who might also run, was at another event after highlighting in his blog how he had helped boost sports in the city.

Jasper Tsang, who earlier said he might contest the top job to offer voters a genuine choice, reiterated he did not have to run if more qualified candidates emerged.