Contract C360 is estimated to be worth around £70m and involves digging two deep access shafts to the main running tunnels at Eleanor Street and Mile End Park.

The shafts, which are scheduled to take three and a half years to finish and M&E fit-out, will provide access for ventilation, maintenance intervention and emergency access to the operating railway.

The winning firm will need relocate a travellers camp, demolish and clear a laundry building at Eleanor Street and relocate a sports pitch and coach park at Mile End Park as part of the enabling works.

The 16m diameter Eleanor Street shaft will descend to 36m, while the 10m diameter Mile End Park will be dug to a depth of 29m.

Firms have until 12 September to register an interest on the Crossrail eSourcing Portal(www.crossrail.bravosolution.co.uk).