The government has signalled that plans to bring a second runway at Gatwick into regular use will get the green light if environmental conditions are met.

Transport Secretary Heidi Alexander said she was “minded to approve” the airport’s plans, but the deadline for a decision has now been pushed back until the end of October.

The main stumbling blocks facing Gatwick’s proposals are related to its provisions for noise prevention and public transport.

The Planning Inspectorate had made recommendations in those two areas after initially rejecting the scheme.

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The airport welcomed the government’s statement but did not say whether it saw a need to adjust its plans to meet the conditions.

Gatwick has until April 24 to respond to the new proposals.

The northern runway already exists at the airport parallel to the main one, but cannot be used at the same time as it is too close.

It is currently limited to being a taxiway and only used for take-offs and landings if the main one has to shut.

Gatwick wants to move it 12 metres further away to solve this problem.

It says being able to run both at the same time would allow around 100,000 more flights per year and create 14,000 jobs.

Gatwick says the £2.2bn project would not need government money, would be 100% privately funded, and could be complete by the end of the decade.

The airport is already the second busiest in the UK, and the busiest single runway airport in Europe.

Campaigners argue the additional traffic would be catastrophic for the environment and the local community in particular.

The Conservatives accused the government of “failing to deliver” and said the decision to “kick the can down the road… shows this promise wasn’t worth the paper it was written on”.

Conservative shadow transport secretary Gareth Bacon added: “Labour are either serious about growth or they are not. This is latest proof that they have no idea how to deliver it.”

Today’s update comes after the chancellor said last month the government also supported a third runway at Heathrow as part of its wider effort to bolster UK economic growth.

However, the formal planning process is still to take place.

Gatwick’s additional runway would be unlikely to open until the end of the decade, assuming any legal challenges were swiftly overcome.

A government source told Sky News: “The transport secretary has set out a path to approving the expansion of Gatwick today following the Planning Inspectorate’s recommendation to refuse the original application.

“This is an important step forward and demonstrates that this government will stop at nothing to deliver economic growth and new infrastructure as part of our Plan for Change.

“Expansion will bring huge benefits for business and represents a victory for holidaymakers. We want to deliver this opportunity in line with our legal, environmental and climate obligations.

“We look forward to Gatwick’s response as they have indicated planes could take off from a new runway before the end of this Parliament.”

Stewart Wingate, Gatwick’s chief executive, said: “We welcome today’s announcement that the Secretary of State for Transport is minded to approve our Northern Runway plans and has outlined a clear pathway to full approval later in the year.

“It is vital that any planning conditions attached to the final approval enable us to make a decision to invest £2.2bn in this project and realise the full benefits of bringing the Northern Runway into routine use.

“We will of course engage fully in the extended process for a final decision.”

He added: “We stand ready to deliver this project which will create 14,000 jobs and generate £1bn a year in economic benefits. By increasing resilience and capacity we can support the UK’s position as a leader in global connectivity and deliver substantial trade and economic growth in the South East and more broadly.

“We have also outlined to government how we plan to grow responsibly to meet increasing passenger demand, while minimising noise and environmental impacts.”

A spokesperson for campaign group Communities Against Gatwick Noise Emissions (Cagne) responded: “We welcome the extension by the secretary of state until October as she has obviously recognised the many holes in the Gatwick airport submissions during the planning hearings.

“Cagne do not believe Gatwick has been totally up front with their submissions, and the planning hearings left so many questions unanswered.”

Greenpeace UK’s policy director, Doug Parr, said of the process ahead: “By approving Gatwick’s expansion the government will hang a millstone the size of a 747 around the country’s neck.

“Such a decision would be one that smacks of desperation, completely ignoring the solid evidence that increasing air travel won’t drive economic growth. The only thing it’s set to boost is air pollution, noise, and climate emissions.”

Ryanair chief executive Eddie Wilson told Sky News the project would do nothing to support growth as there was spare capacity already and claimed the best way to boost the economy was by cutting Air Passenger Duty.

“You have increased taxes in the UK. It’s the airlines that decide on capacity, not the airports,” he said.