'Things got horrifically tense, and Nicole apparently ended up packing her bags and moving out.'
Nicole, 51, and country crooner Keith, 50, have spent huge chunks of time apart, reuniting mainly for the sake of their two daughters, Sunday Rose, 10, and Faith, 7.
GLOBE adds the growing tensions between the power couple has 'spelled doom.'
'Nicole and Keith are always keen to put on a show and tel the world how happy they are,' spills the insider.
'But behind closed doors, it's different story and has been for years.'
The insider further dishes, 'Tensions have lingered and were bound to explode.'
Neither Nicole or Keith have responded to GLOBE's report.