A bone of contention
Definition 1 of 1
Pro Tip 1/3Common Phrases
Often used with verbs like 'become', 'create' or 'resolve' to discuss arguments or disagreements. 
The budget cuts have become a bone of contention in the meetings.
Pro Tip 2/3Neutral Tone
The phrase itself is neutral and doesn't imply who is right or wrong in the disagreement. 
The trade agreement is a bone of contention between the two countries.
Pro Tip 3/3Abstract Use
Can refer to intangible issues, not just physical objects, as the source of dispute. 
Freedom of speech has become a bone of contention.