SCOTTISHPOWER has unveiled plans to spend £5.2 billion to upgrade its ageing power distribution network.

The energy giant, one of the UK's five major suppliers, has submitted plans to regulator Ofgem that it says will also support a transition to a low-carbon economy in the UK.

The company said it would renew and maintain cables that keep the lights on for over 3.5 million customers in Central Scotland, Merseyside and North and Mid Wales.

But it was unable yet to say how much of the 65,000 miles of the overhead and underground network would be upgraded between 2015 and 2023 until inspections are complete.

The investment would also see more than 2500 substations upgraded between 2015 and 2023 to improve services for over 25,000 customers.

Many of the cables and stations were built between the 1950s and 1970s, and are approaching the end of their useful life, the company said. A focus would also be on reinforcing power lines in rural areas to prevent power cuts caused by severe weather.

If the Glasgow-based company is given the green light to invest the cash by energy regulator Ofgem it would be the largest investment by ScottishPower in its distribution network.

The ScottishPower announcement details why it revealed in April that it plans to create 2500 jobs in the next ten years.

That is in addition to 1500 Scottish jobs announced last year, bringing ScottishPower's potential recruitment total to 4000 over the next decade.

Frank Mitchell, chief executive at ScottishPower Energy Networks, said: "We have a unique opportunity to completely modernise our infrastructure. To keep driving improvements and deliver more advanced and smarter infrastructure, which will bring real benefits for customers, we need to invest significantly in our network.

"This £5.2bn investment will create thousands of highly skilled jobs, as we will need a new generation of engineers and technicians to deliver the upgrades.

"We have already started recruiting and we are also investing in partnerships with educational establishments to encourage more people to benefit from the opportunities in our industry."

The firm, owned by Spanish energy giant Iberdrola, said in April that it was investing £4bn in two years up to 2014 in the UK, representing 40% of its global investments, with two-thirds of the investment planned for Scotland.

The announcement comes nearly five months after the company was criticised for increasing service charges to households cut off due to out-standing bills by almost 25%.

In January, ScottishPower, which has 5.2m customers, came under further fire from consumer groups after it imposed a 7% hike in its gas and electricity costs.

It is understood the charges have been increased due to the rising cost of taking legal action against customers who fail to pay their bills.

Ofgem, which is examining the plans to ensure customers are getting the best value, is due to make a decision in November.

ScottishPower also said it would improve its customer services by doubling compensation payments for customers who lose power for extended periods from 2015.

Customers listed on the company's priority services register will also be automatically offered accommodation and hot food if they are without power for more than 12 hours during severe weather.