New and “updated modelling” published ahead of AR7 have revised down the predicted efficiency of wind turbines by more than a quarter, leaving DESNZ plans, and developer funding, looking inadequate.

This is the latest in a series of problematic data, with an investigation into wind farm operators overstating their output, the admission that reliability forecasts were inaccurate, and the recycling of debunked statistics by Scottish ministers.

The Government has revised its official forecasts for the amount of electricity wind farms are expected to generate, reducing the predicted load factor (proportion of time turbines are generating power) for offshore wind from 61 per cent to 43.6 per cent.

The Conservative Party called the energy policy into question, saying it used "bogus numbers", and although there will be some variation year to year on wind power, it makes the £1bn funding in the latest round of contracts unlikely to contribute enough power to meet the Governments targets.

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