Opponents to the Lower Thames Crossing plan are calling for answers over proposed changes to the scheme, which would see less habitat created to compensate for pollution.

National Highways had originally suggested 279 hectares of land at Burham and Blue Bell Hill would be used to compensate for nitrogen emissions, a figure which was reduced to 245 hectares under its official application.

But but under a new “minor refinements consultation” the figure has been reduced to 205 hectares.

A report on the changes says the reduction is due to the impact on existing farmland, and a new “Countryside Stewardship” scheme has now been agreed to help improve existing habitat.

It adds: “The Stewardship scheme focuses on strengthening hedgerow planting and providing greater borders to field margins.

“This new information regarding a Countryside Stewardship means that an increased ecological connectivity would be realised by the Stewardship scheme beyond that assumed in our assessment and so the additional connectivity benefits of our previous proposals would be much reduced.

“It is therefore proposed to remove the Burham site (approximately 10ha) from the Order Limits, which was added after the local refinement consultation and provides less ecological benefit than the retained land.

“It is also proposed to reduce the Blue Bell Hill site by 29ha leaving approximately 43ha within the Order Limits as nitrogen deposition compensation land. The retained land would be the land which maximises the ecological connectivity. Therefore even with the reduction the site meets the function of the compensation land.”

Meanwhile further planned changes include updating plans for utility works at East Tilbury in Essex, to “reduce the amount of land needed”, and to use a single tunnel boring machine to create both planned tunnels beneath the Thames, rather than two machines as previously planned.

But the Lower Thames Crossing Action Group, which is opposed to the scheme, said each aspect of the proposed refinements needed to be fully investigated.

“The LTC Minor Refinements Consultation booklet has so far generated more questions than answers,” said Laura Blake, who chairs the group.

“National Highways appear to be saying that they are removing land from the order limits (the development boundary) that was previously needed and that removing it would not have any affect. However, we are yet to see any evidence to back up these claims, so we will be submitting questions to National Highways.

“We also find it very coincidental that to the north of the river the land being removed from the order limits happens to be the exact bit of land that is in question for a large housing development in the East Tilbury area.

“Some of the info in this consultation seems to be presented in a far more confusing and technical manner than previous consultations, which again generates more questions for us to ask National Highways.”

There are better and more sustainablle alternatives that should be considered

She said the group would also be asking for evidence to support the claim that using one tunnel boring machine would reduce carbon emissions, calling it “hard to believe”.

She added: “Even if it were true the project is still estimated to emit a huge amount of carbon emissions, which is not in keeping with the UK’s commitment to Net Zero.

“We have learnt over the years that you simply cannot take what NH tell you on face value and that asking questions often reveals the realities of the proposed LTC, and the more you look into things and the more questions you ask the worse it usually gets.

“At the end of the day the LTC would still be a hugely destructive and harmful project that fails to meet scheme objectives, would still leave the Dartford Crossing over design capacity, would still be a ‘smart’ motorway by stealth, would still fail against newly set legal targets on air quality, would still fail to meet the new figures for biodiversity net gain requirements, and would still be a waste of £10bn+ of taxpayers’ money.

“There are better and more sustainablle alternatives that should be considered, because we need and deserve better than the proposed LTC.”

In March there were further calls for the scheme to be scrapped, after the Government announced construction would be delayed by two years if the scheme was approved.

The National Audit Office has also raised concerns over its value for money with the estimated costs of delivering the project continuing to climb.

But Matt Palmer, executive director for the Lower Thames Crossing, said: "We're committed to continuing to work with our stakeholders and local community to maximise the benefits of this much-needed new crossing.

“These latest changes improve the design of the Lower Thames Crossing and allow us to reduce the land we need to build and operate it. I would like to thank you in advance for giving us your feedback."

The four-week consultation will run from Wednesday May 17 to Monday June 19 June 2023.

People will be able to respond to the consultation by completing an online survey, completing a paper form or by email.

National Highways is carrying out this consultation now so that improvements to the design can be included in the independent examination of the proposals that is due to begin on June 20.

Following the consultation, National Highways will make a formal submission to the Planning Inspectorate to make a change to the application.

The Planning Inspectorate will then confirm if the changes have been accepted into the examination process or not. If they are accepted they will be examined alongside the rest of the application.

An application for a Development Consent Order was submitted to the Planning Inspectorate late last year and the planning process is currently in the pre-examination phase.

The Planning Inspectorate has confirmed that the examination period will start on June 20 and finish on December 20. A decision is expected by summer 2024.