Plans for a new 5km tunnel into Heathrow "won't affect Hillingdon" and will relieve congestion in west London, Network Rail bosses have claimed.

The first phase of public consultation to build the 5km tunnel, directly linking the Great Western line to Heathrow Airport, has now closed.

Malcolm Parsons, senior programme development manager for the project, said: “Network Rail’s proposal to build a new rail link from the Great Western main line into Heathrow Terminal 5 will improve journeys for millions of people each year, through the provision of a faster, more direct service."

"This service will also help to relieve congestion at Paddington and open up opportunities for thousands of businesses, enabling them to become more competitive and increasing economic growth."

Benefits to the borough of Hillingdon, if plans go ahead, could be reduced congestion on the M4, M25 and the local road network around the airport.

Network Rail says the plans will go ahead regardless of any potential expansion plans at Heathrow.

Mr Parsons added: "Our plans are separate to the additional UK airport capacity proposals currently being explored by the Airports Commission.

"The tunnel is needed to help provide improved rail access to the airport for the whole of the west of the UK."

John Stewart, chairman of Heathrow Association for the Control of Aircraft Noise (HACAN), is uncertain of the effects of the proposed tunnel.

He told getwestlondon: "I think Heathrow want the tunnel anyway but the more rail links the more attractive a third runway will be."

Commercial property experts back the plans, with the tunnel being said to open up 42,000 jobs to the area.

Matt Clarke, a partner at Vail Williams Property Consultants, said: "We can see the traffic issues that growing companies have to battle on local motorways, so we particularly welcome moves to alleviate these problems."

“The elephant in the room, of course, is whether Heathrow’s third runway is approved. But even without that we think this project needs to go ahead – for the sake of residents, businesses and future growth.”

A Heathrow spokesman said: "Heathrow is already the UK’s best connected transport hub. Western Rail access that will build on that strength by transforming journey times to the Thames Valley and beyond, ensuring the whole of the UK benefits from the growth opportunities global connectivity brings.”

Network Rail completed informal public consultations and will now go ahead with the next stage with public consultations this summer.