The Democratic Party has instructed its candidates not to help three Frontier hopefuls campaigning in next month's district council elections.
The ban covers Mok Wai-hung and Ma Siu-kin, both running in Sha Tin, and Lo Chiu-fai, a former Democratic Party member who is standing in Wong Tai Sin.
The party could not support Frontier candidates in Sha Tin because both groups would be fighting in one of the district's 36 constituencies, it said.
Mr Lo was rejected for 'electoral' reasons but the party declined to elaborate.
However, at least one Democrat in Sha Tin has sought support from legislator Emily Lau Wai-hing of The Frontier.
Mr Mok said: 'The Democrats have also sought support from Emily Lau. It's a matter of the breadth of mind. From our point of view, the leading pro-democracy groupings should offer each other support.
