Plans for a motorway interchange to be built near congested local roads in Sydney's inner west are "absurd" says shadow federal transport minister Anthony Albanese.

Mr Albanese wrote to the chair of the WestConnex Delivery Authority, Tony Shepherd, and the NSW Roads Minister, Duncan Gay, last week to ask for a briefing on the plans announced for new M5 East tunnels to emerge at St Peters.

"Beyond belief": Shadow transport minister Anthony Albanese. Credit:Andrew Meares

As Transport Minister in the former federal Labor government, Mr Albanese promised $1.8 billion for the 33-kilometre WestConnex motorway.

But the release of early detail of a major section of that motorway – tunnels to duplicate the chronically congested M5 East – has prompted a backlash from a number of Labor politicians.