The Highways Department says completion of the Hong Kong-Zhuhai-Macau bridge has been put back a year until the end of 2017.
Locally it pointed to problems at the Hong Kong Boundary Crossing Facilities, and the Hong Kong Link Road projects.
The department said there had been difficulties with the "huge and complicated project" with construction and reclamation. It also blamed labour shortages, an unstable supply of materials, environmental requirements and even aviation height limits for the delay.
The government had said earlier this year that a delay in the completion of the bridge was likely.
The Secretary for Transport and Housing, Anthony Cheung, said in January that the end-of-2016 target would be missed in the face of a number of difficulties and challenges.
However, Hung Wing-tat, from the Polytechnic University's Department of Civil and Environmental Engineering, said he was not convinced by the reasons put forward by the Highways Department.
He told RTHK that the construction difficulties and most of the other reasons advanced for the delays were within the government's control and should have been planned for.
"If they haven't done this job then it is serious professional negligence," Hung said.
But he also observed that uncertainties connected with the massive project were not even mentioned. "So I don't know the real reason behind" the delay, he said.
Construction on the bridge began in December 2009. However, due to legal challenges over the environmental impact of the bridge, work on the Hong Kong side did not begin until two years later.
The cost of linking Hong Kong to Macau and Zhuhai will be split between the three authorities. Hong Kong's contribution was estimated at about HK$87 billion, though Hung said this would now inevitably rise.