Richmond Park’s MP Sarah Olney says the admission was made during a community Zoom meeting.
She says residents in Richmond and the surrounding area continue to be plagued by the impact of the ongoing roadworks at Manor Circus.
Nearly 400 residents dialled in to feed back to TfL and the Council, to raise their concerns.
Nick Owen, Head of Network Performance at TfL and Alexander Ehmann, the Chair of the Transport Committee at Richmond Council, apologised.
Mr Owen confessed that TfL had miscalculated the impact on surrounding roads but had moved quickly to rectify part of the situation.
TfL says the work is critical to prevent the further deterioration of the waterproof membrane between the road surface and the roof of the bridge.
This is necessary to prevent a possible catastrophic event, such as concrete falling onto the railway tracks below.
The crossings on all 4 approach roads will also be changed from zebra crossings to signal crossings and greater space made for pedestrians and cyclists.
The goal is to reduce collisions by 50%.
The most disruptive phase should be completed by mid-December.
Cadent Gas have also timed their gas main replacement works to take place at the same time, in order to reduce future disruption.
But The Royal Parks says it has no plans to reopen Sheen Gate.