The King's Cross - Think Again campaign will demonstrate - and possibly speak - at the final planning development committee meeting studying the last elements of the huge Section 106 agreement.
The group has long argued that there are a series of legal reasons why the mammoth mixed-use project ( pictured), masterplanned by Demetri Porphyrios and Allies and Morrison, should not have won planning permission in March.
One key issue for the group is that of affordable housing. The scheme provides for up to 44 per cent of housing on the site to be affordable, but Camden's Revised Unitary Development Plan, adopted as policy in June, requires 50 per cent.
The group says 70 per cent of the affordable stock should be social housing for rent, while the current scheme allows for less than 30 per cent.
'The decision Camden took in March was a provisional one and councillors still have the power to look again at the scheme,' said Michael Edwards, principal spokesman for the campaign.
'Our lawyers have identified several ways in which consent risks being unlawful, but have not received satisfactory answers to many of their points,' he added.