Cyclists in Sydney's inner west will be forced to take "dangerous" detours for at least two years as the state government dismantles a popular bike route for construction of the WestConnex motorway.

The state's transport agency and the contractor building the toll road are tearing up the pedestrian and cycle bridge over Victoria Road near The Crescent intersection as work forges ahead on the controversial $3.9 billion underground Rozelle interchange.

The bike path from the inner west to the city is the state's busiest cycling route. Credit:Louise Kennerley

The agency will also temporarily close a shared bike and pedestrian path that runs from the intersection at Rozelle onto Anzac Bridge, part of the common route for cyclists that links the inner west and the city centre.

Bicycle NSW spokeswoman Bastien Wallace said the alternative routes proposed by the government would divert cyclists from Lilyfield Road along a steep, narrow street in Rozelle and across a two-stage intersection on the City West Link, potentially endangering lives and exacerbating tensions between motorists and cyclists.