The deal includes up to £3bn on new overhead lines and £2.4bn on new and upgraded substations, including design, engineering, construction, and electrical works.

Nineteen winners have been announced for the strategic partnership which will run for an initial five years with the option to extend up to 10.

Nicola Connelly, CEO of SP Energy Networks, said: “We’re delivering the biggest overhaul of the electricity grid ever seen to unlock growth and free up network capacity for new homes, businesses and clean energy projects.

“These strategic partnerships will give suppliers the confidence to invest in themselves, growing their workforce, opening new offices across the country and creating even greater opportunities for the UK

“This is great news for the UK and Scottish supply chains, with every pound spent directly benefiting central southern Scotland and its infrastructure for decades to come.”

SP Energy Networks, part of ScottishPower, owns and operates the transmission network for central and southern Scotland with more than 4,500km of overhead electricity lines, 600 km of underground cables and over 150 substations to transport high voltage power across the region.

It also operates undersea high voltage cables and last week was given the go-ahead to progress with a new underwater superhighway off the east coast of Britain.

In September ScottishPower confirmed it was doubling its investment in the UK to 2028, from £12bn to £24bn, with two thirds focused on electricity networks.

The winning firms are:

Preferred partners to the Strategic Agreement for Transmission Overhead Line Works:

• Balfour Beatty Utility Solutions.
• Cobra Instalaciones y Servicios.
• Keltbray Energy.
• Morgan Sindall Construction & Infrastructure.
• Morrison Energy Services (Transmission Networks).
• Painhas.
• Power Lines, Pipes and Cables.
• Wood Transmission And Distribution.

Preferred partners to the Strategic Agreement for Substation Works:

• Adman Civil Projects.
• Amalgamated Construction.
• George Leslie.
• I&H Brown.
• Keltbray Energy.
• Kirby Group Engineering (UK).
• Linxon UK.
• Luddon Construction.
• Morgan Sindall Construction & Infrastructure.
• Morrison Energy Services (Transmission Networks).
• Northstone (NI).
• Painhas.
• R.J. McLeod (Contractors).
• Siemens Energy.
• UK Grid Solutions.