In the open letter, the think tank said although the Election Committee members it had reached out to in the past two weeks gave them a positive response, all five of its members failed to secure sufficient nominations.

The letter called on Election Committee members to nominate them.

"We are hoping to enrich the political spectrum of the SAR, showcase one country, two systems and contribute to the country and the SAR by running in the upcoming election," said the letter.

Sources said two of its members secured only three nominations by the end of last week with just one week left in the nomination period.

The think tank, headed by Ronny Tong Ka-wah, last week recommended five to run. Maxine Yao Jie-ning, Allan Wong Wing-ho and Jeffrey Chan Chun-hung are hoping to run in geographical constituencies, while Angel Daley Mak Hing-fun aims to run for the legal sector in the functional constituency.

The fifth candidate - who was not announced - will run in the Election Committee constituency.

Real estate and construction sector lawmaker Abraham Shek Lai-him announced that he will not seek reelection due to his age.