Vattenfall had applied in the summer to the Crown Estates, a state property portfolio, to extend Thanet and the nearby Kentish Flats offshore farms. The firm now only intends to add from 10 to 17 turbines to the 30 already installed at Kentish flats.

The decision was principally because "the indicated timescales for the necessary grid upgrades to support a viable extension fall outside the timescale set by Vattenfall for constructing an extension under the current Crown Estate leasing round", said the company in a statement.

“Our decision in respect of the Thanet project will no doubt come as a disappointment to many local people and has not been taken lightly given our strong relationship and commitment to the Thanet area,” said David Hodkinson, Vattenfall’s head of development.

“We hope there will be a future opportunity to return to the possibility of an extension to the Thanet project, but for now we will focus on operating the existing project safely and productively.”

The £780m ($1.2bn) Thanet wind farm opened on 23 September. Its 100 turbines have a combined capacity of 300 MW, making it the world’s largest offshore plant.  Kentish Flats is one of the UK’s earliest wind farms, dating back five years.

Vattenfall has 526 MW of onshore and 688 MW of offshore installed wind capacity across northern Europe. It is currently building eight wind farms in six countries.