Two Labour London Assembly members have tabled a motion urging Mayor of London Sadiq Khan to refuse to sign a guarantee to meet the Garden Bridge's maintenance costs.
Former Mayor of London Boris Johnson agreed in principle that the Greater London Authority would serve as guarantor of the £3 million-a-year running costs of the controversial Garden Bridge if private fundraising falls short.
His successor Sadiq Khan has repeatedly said that he won't give his approval to the guarantee unless he can be sure that it won't be called upon.
Labour London Assembly members Tom Copley and Florence Eshalomi have tabled a motion which will be debated at City Hall on Wednesday 8 February.
The motion says: "This Assembly welcomes the Mayor's commitment that no further public money be spent on the Garden Bridge project and believes that the best way for him to ensure this is by refusing to sign the guarantee of the bridge's running costs."
The Garden Bridge has faced criticism from Assembly members of all parties represented at City Hall – Labour, Conservative, Green, UKIP and Liberal Democrat – and the motion seems likely to be passed.
If the motion is passed it will not be binding on the Mayor, but the fact that it has been tabled by two of his Labour colleagues at City Hall will increase the political pressure on Mr Khan.