The two jobs cover track and overhead catenary system works, and tunnel and lineside M&E and ventilation works.

HS2 aims to shortlist four bidders for each of the packages, which should be let before the end of next year.

The successful bidder for the £1.55bn OCS package will oversee HS2’s construction and its dynamic testing phase, linking the whole system and trains.

This includes essential infrastructure, including the overhead catenary ‘power’ system from which high speed trains will draw down power, and 180 miles of track along which they will travel at speeds of up to 225mph.

The vast contract also includes construction work within stations and in tunnels including supply of engineering trains to link worksites as well as design integration and co-ordination with other railway systems, civil engineering and station construction contractors.

The second £330m contract package is for the tunnel and lineside M&E and ventilation works.

It covers the design, installation, testing and commissioning of HS2’ safety equipment including tunnel ventilation fans; lighting; handrails; fire safety equipment and tunnel alarm systems.

There are nine tunnels in phase 1 of HS2 running to around 30 miles.

HS2 chief executive Mark Thurston said: “We’re looking for the smartest, most cost effective solutions that the industry has to offer through these contracts.

“These two essential contracts are fundamental to HS2 operating safely, reliably and efficiently for the millions of people who will use and come to depend on it. ”

Access to the tender document is restricted. More information is available from  HS2 Procurement tel: 02079446392 or be email.