bone of contention
Pronunciation:
/ˈbəʊn əv kənˈtɛnʃən//ˈboʊn əv kənˈtɛnʃən/noun
Definitions
Something that continues to be disputed; something on which no agreement can be reached
Example: It is still a bone of contention whether to go ahead with the original plan in light of the new evidence.