Peel Energy and United Utilities want to add a further 16 turbines at Scout Moor, on land between Rochdale and Rossendale.
Rossendale Borough Council's development control committee gave the go-ahead for 14 of them at a meeting on Tuesday night.
Councillors in Rochdale are yet to rule on plans for the remaining two.
A statement from Rossendale Borough Council said their decision will now be referred to the government, which will then decide whether or not to "call-in" the decision for further debate.
Scout Moor wind farm opened in 2008 with 26 existing wind turbines generating enough electricity for 40,000 homes.
MW = Megawatts
Source: RenewableUK
However, opponents are concerned the expansion of the wind farm will impact negatively on the natural beauty of the area.
Proposals to double the size of the site have already been scaled down after a public consultation.
A joint planning application for expansion on Scout Moor and the neighbouring Rooley Moor was submitted to Rochdale and Rossendale Borough Councils.
The document states "if all the proposals... are consented they will result in the largest wind farm in England".
Jon England of Peel Energy said: "The UK is quite a highly populated country. Offshore is one of those areas which moves it away from communities but you are going to increase costs.
"If you increase the cost of construction of these sorts of developments you are going to increase the cost to the consumer.
"We've been out to the community many times. We've done tens of consultation events. Yes there is objection [to expansion].
"But in the scale of the population that see Scout Moor wind farm the level of objection is relatively low."

Media playback is not supported on this device
Liverpool cancelled a meeting with Sterling on Friday because of comments attributed to the player's agent.
Aidy Ward reportedly said the England forward, 20, will not sign a new deal even if offered "£900,000 a week".
Rodgers said: "Raheem has two years left on his deal and I expect him to see that two years through."
Rodgers said Sterling would be available for selection for the team's last game of the Premier League season against Stoke on Sunday and insisted the player would not be unhappy with the prospect of having to stay at the club.
"We want to resolve the situation but it doesn't change my approach to him. There is no problem there," he added.
Radio 5 live: Phil Neville is teased for his club loyalty
"I don't see Raheem being unhappy. Raheem's representative made it very clear that he wanted to speak at the end of the season.
"Our concentration is on the last game of the season and I'm sure talks will take place over the course of the summer."
The England international has already rejected a new £100,000-a-week contract with the club and was expected to tell Rodgers and chief executive Ian Ayre at Friday's cancelled meeting that he wanted to leave this summer.
Media playback is not supported on this device
Ward told the Evening Standard that he did not care about the PR of the club and used a four-letter expletive to describe former Liverpool defender Jamie Carragher, who has criticised the player.
"He's not signing for £700,000, £800,000, £900,000 a week," said Ward in the newspaper interview.
But Rodgers said the club would attempt to continue with contract discussions "as private as possibly can be".
"Whatever conversation I have with a player or member of staff will remain between us," added the Northern Irishman.
"The owners have shown their strength in their time here. When they have had to show that strength with players they have done that."
Planning permission has been granted to create what is believed to be England's largest onshore wind farm.
[NEXT_CONCEPT]
Liverpool manager Brendan Rodgers has said he expects forward Raheem Sterling to stay at the club for the remainder of the two years on his contract.