An MP has officially withdrawn his support for plans to erect a multi-billion pound theme park on parts of a protected nature site.
It comes amid ongoing concerns over transport infrastructure, local businesses threatened with eviction and the site's new-found status as a nature haven.
Billed as the UK's answer to Disneyland, the £2.5bn park aims to be one of Europe's largest leisure and hospitality offerings with more than 100 hectares of marshland – equivalent to 140 football pitches – set aside for rides, hotels, bars and other event spaces.
The developers, London Resort Company Holdings (LRCH), claim the attraction will transform a "largely brownfield former industrial site" and create nearly 50,000 jobs.
But Mr Johnson, who had initially entertained the prospect of the park, says he has now "lost confidence" in the developer's ability to deliver.
The Tory MP said: “This project has the potential to totally change the character of the local area, therefore it was essential that the developers, LRCH fully engaged with local residents and brought people with them. This is something they have failed to do.
“I have repeatedly told LRCH of how they needed to immerse themselves into the local community and ensure people were fully aware of their proposals and how it would affect the local area, yet this has not happened.
"Many of us were excited when this proposal was first made public. There could have been huge benefits to the area, if the project was approached in the right way.
He added: "Instead, we have seen endless delays and uncertainty for local residents and businesses in the area.
"Enough is enough. Sadly, I have lost confidence in the ability of LRCH to build this theme park in a way that would enhance Dartford."
Besides a perceived lack of local engagement, the theme park project has also been blighted by environmental issues.
Campaigners have raised more than £50,000 to cover legal bills to fight the proposals on the Peninsular.
It comes after the site was confirmed as a site of special scientific interest (SSSI) owing to its rich abundance of grassland, wetlands, birds, and invertebrates – including one of the rarest spiders in the country.
The move recently prompted the BBC and ITV, who had provisionally lent image rights to the project, to scrap their involvement.
Mr Johnson said he had "serious concerns" over the impact the Resort would have on wildlife and traffic.
The government whip said: "We all know the traffic problems Dartford suffers from and I am not convinced the theme park’s traffic could be adequately managed.
"I am also seriously concerned over the impact the park would have on the wildlife on the peninsular.
"The area is rapidly becoming a vital habitat for a wide range of birds and other animal species and any theme park would have a serious impact on this."
The Tory MP added: “In short, Dartford can do better than this theme park.
“We can ensure the Swanscombe peninsular provides a wonderful wildlife haven here on our doorstep for us and future generations to enjoy.”
Firms operating on nearby industrial estates included in the park's blueprint also face the threat of looming eviction under controversial compulsory purchase powers.
Business owners likened the uncertainty, which has dampened investment and growth opportunities, to "like being on death row".
Mr Johnson, who now hopes the developers will withdraw their bid, added: "The uncertainty the project has brought to the area is holding back businesses that want to plan for their future.
"Far from being the job provider we all hoped for, it is actually costing jobs."
His comments come ahead of a preliminary meeting of the Planning Inspectorate, the body tasked with assessing the application, due to be held at the end of this month.
The London Resort was the first commercial venture to be designated as a “nationally significant infrastructure project” by the government.
It means developers can bypass local planning processes and go straight to the Secretary of State for housing, communities and local government to seek consent for the project.
If built, it will be the first European development of its kind to be built from scratch since the opening of Disneyland Paris in 1992.
Developers are planning to open the park in two stages with the first "gate" opening in 2025 and the second within five years.
The resort will feature a range of themed rides, dining experiences and an eSports arena with around 70% of its attractions undercover.
Planners claim it will be one of the most sustainable, global destinations in the world and the first operationally carbon neutral theme park.
Yesterday the company announced it was entering the "next phase of the company's capital raise" - in other words, seeking the huge investment needed to make it a reality.
It welcomed two new board members but saw long term stakeholder, Kuwaiti businessman and Ebbsfleet United owner Abdulla Al-Humaidi step back from the board.