Legal heavyweights slammed as unfair the so-called "primary election polls" conducted by the opposition camp over the past weekend because they gave a head start to opposition candidates.

They also said the candidates' attempt to paralyze the government after taking control of Hong Kong's governance could violate the National Security Law.

Dubbed the "35-plus primaries" by the opposition camp, the political maneuver was designed to narrow the number of opposition candidates in the upcoming Legislative Council election in September in the hope of securing a majority in the legislature.

The "primaries", which were held a week before the official Legislative Council candidate nomination period begins, have since drawn sharp criticism from legal experts, who said the polling offers an unfair advantage to the opposition camp in the election by allowing it to launch its election campaigns sooner.

"The so-called opposition camp 'primaries' are unfair to all other possible candidates," said Ronny Tong Ka-wah, Hong Kong senior counsel and executive councilor. "It steals a march on all other candidates by starting an election campaign earlier."

The legitimacy of the "primary polls" was also questioned. Willy Fu Kin-chi, vice-chairman of the Hong Kong Legal Exchange Foundation, said the "primaries" did not uphold the key principles of "openness, fairness and honesty".

Fu described the "primaries" as a dishonest "black box" operation, as many aspects of the elections were not made public, and the system and organizer couldn't avoid multiple voting, which was in fact prevalent.

Former Hong Kong chief executive Leung Chun-ying also underscored the issue. In a social media post on Monday, Leung said anyone could use a made-up Hong Kong ID card number to vote in multiple districts during the "primaries".

Tian Feilong, an associate professor at the Law School of Beihang University, also criticized the opposition camp's "primaries" for advocating "political mutual destruction", and creating a misleading illusion of biased, extremist public opinion.

The results of "primary polls" were not recognized by Hong Kong's laws, they could have a damaging effect on the special administrative region's democratic electoral process by creating a distorted illusion, Tian said.

The "primaries" are another attempt by Benny Tai Yiu-ting, a leading figure of the opposition to paralyze the government, Fu said. "The plan is to cause a paralysis in government operations by vetoing the upcoming fiscal budget," Fu said, adding that this could breach Articles 22 and 23 of the new National Security Law, and opposition candidates could be disqualified because of it.

According to Article 22 of the National Security Law, subversion acts include seriously undermining the performance of duties and functions in accordance with the law by the body of power of the Hong Kong SAR.

In a televised interview, Basic Law Committee member Priscilla Leung Mei-fun said the opposition candidates who participated in the "primaries" have violated not only the National Security Law, but also the Basic Law.

Those from the opposition want to take over Hong Kong's governance power, not to improve the special administrative region, but to paralyze the city, Leung said, adding that this has obviously breached the National Security Law and Basic Law.