A £1 billion wind farm in ­Scottish waters that would be the third largest in the world has been given the green light.

Up to 326 turbines are to be built off Caithness after ministerial approval was granted for two neighbouring large-scale projects.

Together they will potentially generate electricity for more than a million homes and provide work for up to 4600 people during the construction phase and 580 once in operation.

Harbour towns around the Moray Firth and Caithness are hoping for an economic windfall and the government claims the development could be worth £2.5bn to the Scottish economy.

Some of the turbines at the Moray Offshore Renewables Limited and the Beatrice Offshore Windfarm Limited projects will be only eight miles from the shore..

But there remains some ­uncertainty over the project as one of the main developers, SSE, is currently reviewing its offshore strategy, blaming UK Government subsidy decisions.

The consents are subject to strict environmental conditions, but RSPB Scotland is warning the overall scale of the joint development represents too great a threat to Scotland's wildlife. Fishermen are also seeking reassurances.

Concerns from the Ministry of Defence that the turbines could interfere with radar at RAF Lossiemouth have been addressed.

Announcing the decision ­yesterday, Energy Minister Fergus Ewing said: "Offshore wind has been delayed by the process of the UK Government's Electricity Market Reform, but these two consents today offer tangible progress towards real investment opportunity in Scotland."

He said the government was committed to the successful and sustainable development of an offshore wind sector, which could lead to a potential inward investment of £30bn and support up to 28,000 direct jobs and a further 20,000 indirect jobs, generating up to £7.1bn for the economy. He added: "The Scottish Government wants to see the right developments in the right places and Scottish planning policy is clear that the design and location of any onshore and offshore wind farm should reflect the scale and character of the landscape or seascape and should be considered environmentally acceptable."

Lindsay Leask, senior policy manager for industry body Scottish Renewables, said the first ever consent for a large-scale commercial offshore wind farm in Scotland was an important step forward for the industry.

Dr Richard Dixon, director of Friends of the Earth Scotland, welcomed it as "great news", adding: "These two schemes alone could provide 40% of Scotland's peak power needs on a windy day."

However, Aedan Smith, head of planning and development at RSPB Scotland, said: "It is disappointing Scottish ministers have decided to take such a risk with Scotland's internationally important populations of seabirds. We will be looking closely at the details of the consent over the next few days but we believe a smaller development could have provided very significant amounts of renewable energy with much less risk to marine wildlife."

Bertie Armstrong, chief executive of the Scottish Fishermen's Federation, said fishermen would have preferred no such large-scale interference from turbines, but added: "Accepting that such developments are going to happen over the coming years, it is absolutely essential the fishing industry continues to be fully consulted during the complicated planning and licensing processes so the impact of offshore renewables on fishing is mitigated."