A bold plan to build a multi-million-dollar bridge to Kangaroo Island from the mainland of South Australia has been rubbished by the island's Mayor, who described the proposal as a "bridge over troubled waters".

The four-lane bridge has been proposed by the Universal Bridging Consortium — an umbrella for a group of companies working together to initiate, plan and deliver the megaproject — and has been endorsed by SA Best MP Frank Pangallo.

The bridge would have a length of about 14 kilometres and would be built across Backstairs Passage.

If built, the bridge would be one of the longest overwater vehicle bridges in Australia.

The world's longest overwater bridge is the Jiaozhou Bay Bridge in Shandong Province, China — with a length of 42.2km.

The proposed bridge would be 14 kilometres long. ( Facebook: Universal Bridging Consortium )

Local mayor talks down chances

The proposal has been categorically dismissed by Kangaroo Island Mayor Peter Clements who described the idea as "a bridge over troubled waters".

"In any case the island people are not going to stand for this," Mr Clements said.

"We're trying to protect something very, very precious over here on Kangaroo Island and this is all about our branding and about doing the right thing by the island.

"A bridge is not going to do that, a bridge is just going to put money in the hands of a few people.

"It's a huge road toll, would put the ferry businesses out of business and it would just create a mass tourism exercise for Kangaroo Island that, quite frankly, is not what we want."

Access is 'holding Kangaroo Island back'

But Mr Pangallo has called on the State Government to consider the proposal put forward by the consortium, and believed that a lack of accessibility was "holding Kangaroo Island back".

The new KI Connect catamaran ferry to Kangaroo Island. ( Supplied )

"The concept is quite doable and it's something that we need to actually start to consider for the future of the South Australian economy, the Kangaroo Island economy," Mr Pangallo said.

"It's a 14-kilometre-span bridge and would cost somewhere between $4 to $5 billion dollars."

A return ferry trip to Kangaroo Island can cost upwards of about $400 for a family of four and a vehicle, or about $300 per person by plane.

'Australia's number one tourist destination'

The bridge would cut travel time from 1.5 hours to just 15 minutes. ( Facebook: Universal Bridging Consortium )

Mr Pangallo said that by considering the proposal, the State Government would be "opening up" the island to a boost in tourism.

"What this bridge would do would make Kangaroo Island Australia's number one tourist destination," he said.

"What this does is just opens up a whole new world of opportunities for South Australia and the island.

"Even the bridge itself would be one of the wonders of the world.

"It's one of those futuristic visions, I'm not saying it has to happen today or tomorrow.

"I think it's something that the Government of the day needs to consider."

Mayor says there are a lot of 'social issues'

But Mr Clements said those on the island would fight the proposal, and didn't believe it would go ahead.

He said the proposal was only at a conceptual stage and had a lot of engineering and social issues to get passed.

"I don't think it will be difficult, our voice will be very, very loud if they do attempt to go to the next stage," Mayor Clements said.

Kangaroo Island is home to about 4,200 people. ( South Australian Country Hour: Marty McCarthy )

"I don't believe they will ever get a social licence to build a bridge to Kangaroo Island and I think that's going to be critical to them and to any investors."

The consortium has called on the State Government to make a financial commitment of about $100,000 to commence a pre-feasibility study.

Under the proposal, the bridge would be built south of Cape Jervis on the Fleurieu Peninsula, and land south-east of Penneshaw.

The State Government has been contacted for comment.