Chen Xinxin, a researcher with the Chinese Academy of Social Sciences in Beijing, urged Hong Kong to set political differences aside and think seriously about the direction of future development.

“Guangdong might not want to admit it, but it is well prepared to go solo in case the Hong Kong factor does not work,” Chen said.

Qu Jian, deputy director of the China Development Institute, a Shenzhen-government think tank, who also led research on the Shenzhen-Zhongshan bridge, a 51km, eight-lane link that is expected to be completed by 2021, said there had always been a plan B in place.

“Whenever it comes to cross-border planning projects, we are fully prepared that Hong Kong is always going to go slower and we always have a plan B that is to focus on what we can work on first and wait for Hong Kong to catch up,” Qu said.

Guangdong has pushed aggressively for greater integration with Hong Kong but has achieved only limited results, partly due to growing fears in Hong Kong that it could lose its high degree of autonomy and related freedoms, as well as the different planning and public consultation processes on either side of the border.

Guangdong governor Ma Xingrui received a briefing last month from a prominent Beijing think tank’s on its study findings and recommendations for the Greater Bay Area, and Guangdong media reported that the provincial authorities had sent a draft urban plan to Hong Kong for comment.

But Albert Lai Kwong-tak, policy convener at the Hong Kong-based think tank Professional Commons, said professional and public engagement were key for such a major regional plan to work, and he was concerned about the lack of it in the Greater Bay Area planning process.

“How can such a major policy, with such a long-term impact on Hong Kong, leave out the voices of the public? International examples tell us a top-down approach will never work,” Lai said.

Guangdong researchers also said they had little clue what Hong Kong’s next administration might have in mind for the plan.

Carrie Lam Cheng Yuet-ngor will become Hong Kong’s next chief executive on July 1, leaving her new team barely three months to finalise its proposal.

“So far, the incoming chief executive has yet to reveal her thinking on the Greater Bay Area. Just exactly how familiar Hong Kong’s new administration will be with regional integration is also a concern,” said Professor Lin Jiang, an expert on the mainland’s pilot reform zones at Guangzhou’s Sun Yat-sen University. “Will it be her way or [outgoing Chief Executive Leung Chung-ying’s] way?

“The current situation puts Hong Kong in an awkward position.”

The chief executive-elect’s office declined to comment on the mainland researchers’ concerns or on existing government policy.

A spokesman with the Constitutional and Mainland Affairs Bureau said Hong Kong’s participation in the drawing up of a Greater Bay Area plan would be based on “one country, two systems”and a plan would be finalised “within the year”.

“The HKSAR Government will continue to engage relevant professional groups and advisory committees and reflect their views in our submission to the NDRC,” he said.

Lin said he was worried Hong Kong might play a passive role in the integration scheme.

“There have been few breakthroughs over the years for cross-border development, with both sides mostly running through procedural matters,” he said. “Hong Kong’s political reality and resistance to integration with the mainland have dampened the enthusiasm of local Guangdong leaders.”

Professor Zhang Guangnan, an expert on cross-border collaboration at Sun Yat-sen University, said the Greater Bay Area plan was meant to break up city barriers in the Pearl River Delta to boost growth and allow test runs of creative reform measures on institutional and public administration as well as economic and infrastructure development.

“This is a unique development model unseen anywhere around the world, as the region involves [the] one country, two systems [principle], three different currencies, three independent members of the World Trade Organisation in different customs territories,” Zhang said.

Tian Feilong, an associate law professor at Beihang University in Beijing, called on Hong Kong to develop a sense of crisis because “national development strategies will pace ahead with or without Hong Kong’s participation”.

“The home field is on the mainland side. Hong Kong needs to make a rational decision whether it wants to play a part or not ... if Hong Kong is so passive, to the level that it is obstructing national strategic development, the policy will be leaning to favour Shenzhen and Macau to replace Hong Kong in terms of industry positioning,” Tian said.

But some say that viewed in the light of institutional differences, Hong Kong should not be seen as the sole party to blame.

Chen Guanghan, director of Sun Yat-sen University’s Centre for Studies of Hong Kong, Macau and the Pearl River Delta, said the mainland had yet to open up in many areas such as the financial market or free flow of information.

“It is still hard to foresee barrier-free access to Facebook in the Greater Bay Area region,” Chen said. “When something is threatening national security, it can never go ahead.”