The U.K. needs to ramp up construction of new nuclear power plants to meet its ambitious 2050 targets on cutting greenhouse gas emissions and secure the country's independence from oil and gas imports and volatile prices, the U.K.'s former chief scientist said Thursday.

The best energy mix for the U.K., which is facing growing gas imports as domestic North Sea hydrocarbon reserves dwindle, is for 50% to 60% nuclear power by 2050 with gas, micro-generation, solar, wind, energy efficiency and other low-carbon technologies comprising the rest. This scenario assumes that transport and heat is mostly electrified by then to cut emissions.

The U.K. government, which has legislated an 80% cut in emissions by 2050 versus 1990, needs to come up with a long-term energy strategy as soon as possible as the cost of energy imports is creating a huge strain on the U.K. economy, said David King, director of the Smith School of Enterprise and the Environment at the University of Oxford.

"The market place is surprisingly weak at providing the energy we need without a long-term strategy. If we invest incorrectly over the next five years, we won't get the energy mix we need," said King, who authored a report published Thursday on meeting the targets.

King said that it's possible to place 27 new nuclear power stations by 2050 on sites where there are already nuclear facilities.

Public support for new nuclear is currently quite high in the U.K., particularly around the sites where existing nuclear power plants are located as many jobs depend on the facilities.

The U.K.'s 17 nuclear reactors currently generate around a fifth of the country's electricity, but most of those power stations are aging and are due to close over the next decade.

Plans by major European utilities to build 16 gigawatts of new nuclear in the U.K. by 2050 would mostly only replace retired capacity.

Around a quarter of the U.K.'s electricity generating capacity is being shuttered over the next decade as aging nuclear plants are closed and coal plants are retired due to European Union environmental legislation.

Energy regulator Ofgem has estimated that around GBP200 billion investment is required to 2020 in new power stations and upgrades of grid and network infrastructure to keep the lights on while meeting EU climate change targets.

The U.K. government has placed big bets on wind energy coming from giant offshore installations far off the British coast, but King said the costs of constructing and maintaining these wind farms would be "massive." Wind farms also require investments in gas-fired power stations as back up when the wind isn't blowing.

"That increases the capacity costs of using the wind farm," he said.

King dismissed the prospects of a European shale gas boom that would bring down regional natural gas prices and avert the need for gas imports for power generation, as has been the case in the U.S., saying it was unlikely due to environmental reasons in what is a very densely populated region.

-By Selina Williams, Dow Jones Newswires; +44 207 842 9262; selina.williams@dowjones.com