Grant Shapps is served with notice of potential action and has been asked to respond within 10 days
A legal challenge is being launched to halt government plans for a two-mile tunnel under Stonehenge that will cut through a world heritage site.
Earlier this month the transport secretary, Grant Shapps, approved the £1.7bn project, which will include 8 miles of extended dual carriageway along the A303 in Wiltshire.