“I went to [the protest] by myself, as I hate abuse of privilege,” Chu told Commercial Radio on Monday morning.

He claimed at the protest that the airline worker who allegedly spoke on the phone with the city leader was “in tears” after the conversation.

He said he had been told more details by a Cathay Pacific worker close to the matter.

“It was an accidental [meeting]. I bumped into her when having lunch on Saturday. I think what she said was trustworthy,” said Chu.

“No one in Hong Kong should be stopped from speaking the truth because of special privilege…I will pursue the matter until the end. This is a big deal,” he said, adding that he was not targeting Leung personally, but the abuse of privilege.

While Transport Minister Professor Anthony Cheung Bing-leung has requested the Airport Authority report on the saga, Carol Ng Man-yee, general secretary of the Hong Kong Cabin Crew Federation, said it was not politicising the matter, as it was concerned with aircraft safety.

Meanwhile, convenor of Loving Hong Kong Voices Ko Tat-bun said the situation had been exaggerated, and was an opportune attempt to create chaos.

“Has Leung abused his power? It is abuse only if he has repeatedly done so,” said Ko on RTHK on Monday morning.

Cheung Shu-wang, chairman of the Staff and Workers Union of Hong Kong Civil Airlines, said it was “not the first time” airport staff had delivered left luggage to passengers in closed-off areas. “This is an airline service, [rules] have not been written down in black-and-white,” said Cheung.

This is not the first time Chu has criticised Leung.

In the four years up to Hong Kong’s handover in 1997, the pair served in the Preliminary Working Committee and the Preparatory Committee, which helped the Chinese government prepare for the city’s return to the mainland.

In the run-up to the chief executive election in 2012, Chu criticised both Leung and his arch-rival Henry Tang Ying-yen.

In November 2011, Chu wrote in his column in The Sun that it was “disobedient” for Leung to run for the top job since Beijing wanted Tang to win the poll.

But a month later, in an article on the bloggers’ website Professionals Online, he accused Tang of lying about his education.

Chu said Tang was not a person of integrity, as he claimed in the 1990s that he got his master’s degree from Yale, but had in fact not finished his studies there.

At the time, a spokesman from Tang’s election office said that after he was appointed secretary for commerce and industry, he clarified that he did not finish Yale’s master’s programme because he had to help with his family business in Hong Kong.

But immediately after Leung won the top job, Chu criticised him again, claiming that from his 30-year acquaintance with Leung, he knew he was “an ambitious and ruthless man who conceals his personality”.

In 1992, Chu made a name for himself by opposing then governor Chris Patten’s electoral reform package for the 1994-1995 elections. Beijing lashed out the last governor’s proposal to give more than a million electors a vote in nine new functional constituencies, accusing him of breaching the Basic Law and previous Sino-British agreements.

But in June 2004, Chu, then a lawmaker and a local deputy to the National People’s Congress, made headlines again by submitting a list containing the names of a dozen democrats to senior mainland officials responsible for Hong Kong affairs.

He suggested the central government issue home-return permits to them to clear the way for talks with mainland officials. But there was no breakthrough afterwards.