Hong Kong and Shenzhen together can form a world-class metropolis by enhancing the flow of passengers, goods, capital and information between the cities, a report has said.

After an eight-month research project, experts from the Bauhinia Foundation Research Center, a local think tank, said that if the cities were to work together, they could boost their combined GDP by $1.1 trillion by 2020.

While there was obvious competition between the two cities, working together would be mutually beneficial, the experts said.

The center's report looked at the feasibility of building a Hong Kong-Shenzhen metropolis.

Researchers spoke to government officials and businessmen from both cities, as well as more than 1,000 Shenzhen citizens.

Among the key recommendations was the formation of a "Hong Kong-Shenzhen living sphere", with all areas accessible within one hour.

The report also proposed the cities carry out a study on the connection of their airport rail links with a view to creating a "super airport hub".

Another key recommendation was to allow Shenzhen residents to travel freely to a "special business zone" in Hong Kong.

To facilitate the smooth flow of people, it suggested Shenzhen citizens be issued with electronic entry permits which they can use to make multiple visits to Hong Kong within a fixed period.

At the same time, it was suggested that entry visa application fees be lowered or cancelled, while the time for document checks for mainland travelers should be reduced to 15 -20 minutes.

"The governments of Hong Kong and Shenzhen are both very supportive of the overall direction of our study," the center's chairman Anthony Wu told a press conference yesterday.

"When we talk about molding the two cities into a metropolis, we are aiming for a win-win solution, with no such thing as a winner and a loser," he said.

"If we join hands to build a metropolis, we will attract more foreign investors and multinational corporations to open regional centers here.

"Of course there is competition between us, but healthy competition combined with cooperation will make the pie bigger and benefit both of us," he explained.

Zhu Wenhui, a consultant to the research group, said at present, Hongkongers can travel freely to Shenzhen but people from Shenzhen have to get a visa to enter Hong Kong.

The mutually free flow of people was necessary for the two places to complement each other, he said.

The proposal to allow Shenzhen citizens to visit Hong Kong on multiple electronic permits was not a fully free system because they would still have to apply for visas, Zhu said.

Only those who go to Hong Kong for shopping, entertainment, holidays or business are issued multiple entry visas, but they cannot hold jobs in Hong Kong, he said.