The northern section of the North-South superhighway, already open between Elephant and Castle and Blackfriars, runs via Saffron Hill and Bloomsbury to King’s Cross.
A spokesman for Labour mayoral candidate Sadiq Khan said: “Sadiq is committed to implementing the next phases of the cycle superhighway, but it is really important we learn from previous phases. We need to avoid repeating the same mistakes and must do more to minimise upheaval caused during any new construction.”
A spokesman for Tory candidate Zac Goldsmith said he “would continue” Mr Johnson’s £913 million investment in cycling, and added: “Zac supports cycle superhighways.”