Argent's ambitious King's Cross redevelopment could face a judicial review after local groups called Camden Council's handling of the application 'flawed'.
The disagreement is over the amount and type of housing proposed for the so-called 'triangle development'.
The council has agreed in principle to the project, voting in favour of a 'minded to approve' decision, subject to a Section 106 agreement which is still under discussion.
However, the community consortium, King's Cross Railway Lands Group, claims the amount of affordable housing planned in the redevelopment falls short of the borough's latest policy.
It has also questioned the justification for the proposed demolition of some listed buildings and the amount of office space.
In addition, the consortium is unhappy with various environmental aspects of the redevelopment. It claims the scheme should have been subject to a strategic environmental assessment.
In reply, the council said it will 'respond to this pre-action as necessary'.
A Camden spokesman said: 'We have worked extremely hard to ensure the planning process has been carried out correctly.
'We have set the highest standards for its technical accuracy and professional assessment, and we have carried out an extensive consultation.' by Richard Vaughan