London Assembly member Murad Qureshi has written to the City of London Corporation to receive assurances over mayor Boris Johnson's plans for the £60m London River Park.
Qureshi has highlighted three "major navigational concerns" relating to the project, which include whether the Thames will continue to allow two-way traffic along the river.
Other concerns include whether the proposed floating walkway will be able to withstand the impact of a vessel and whether barge access will be secured between Southwark Bridge and Cannon Street.
Qureshi said: "Unfortunately, the mayor was not able to reassure me and the many others who have serious concerns about the safety logistics of this plan."