Luton Borough Council has announced it will launch a High Court challenge after neighbouring Central Beds Council approved plans for a new M1-A6 link road north of the town.
The £64.6m project would link junction 11a of the motorway to the A6 Barton Road.
Legal proceedings were agreed by LBC's executive committee at a meeting held in private last night (Thursday).
The plans are for a new two-and-three-quarter mile single and dual carriageway road, with the decision issued by Central Beds on January 10.
Luton South Cllr Paul Castleman, portfolio holder for planning, said: “We have made four objections to the planning application and spoke at the planning committee meetings.
"We wrote to the Secretary of State for Housing, Communities and Local Government requesting that they call-in the M1-A6 planning application for his determination, however the Secretary of State declined to call in the application.
“Central Bedfordshire Local Plan examination inspectors questioned whether a link road was needed.
"The Inspectors’ letters have not been properly considered in determining the planning application.
"Therefore we have no option other than to proceed with a JR”.
The first stage of the process is the High Court considering whether there is an arguable case. If so, it will grant permission for the claim to proceed.
In response, a Central Beds Council spokesman said: “It is deeply disappointing that Luton Borough Council is intending to challenge the decision-making process for the M1-A6.
“This action will result in significant legal bills having to be paid from public funds.
“It will also jeopardise significant government investment in an important piece of infrastructure for our area.
“The benefits that this link road will bring, to residents of both Luton and Central Bedfordshire, are considerable. It will relieve congestion and reduce HGVs from other routes. It will spur business growth and jobs.
"And it will as support much needed new homes, including homes specifically to meet Luton’s unmet need.”
A rail freight interchange forms part of the scheme, while a new roundabout is proposed at the new road's junction with the A6 Barton Road.
The 170-acre site is mostly arable farmland within the Green Belt and contains two areas of ancient woodland, Sundon Wood and George Wood.
CPRE Bedfordshire, the Chilterns Conservation Board, Natural England and the Woodland Trust objected to the development, while the Wildlife Trust and the Crown Estate expressed concerns.
Streatley Parish Council supported the application with some concerns, but Sundon, Chalton, Harlington and Barton-le-Clay parish councils all opposed it.
The Chilterns Conservation Board is also thought to have been considering whether to seek a judicial review.
LBC lost a previous case against Central Beds in the Court of Appeal (civil division) in 2015 over planning approval for the site known as Houghton Regis North 1.
That scheme was for outline planning permission to develop 647 of open fields, in the Green Belt, immediately to the north of the Luton, Dunstable, Houghton Regis conurbation.