This is a phrase used by politicians and others when they want to convey:
1. that they disagree politely
2. that they disagree strongly and think what has been said is 'rubbish'.
3. that they disagree, but in a way that implies they are letting others (who may also disagree) know that they recognise/or offer a common position.
4. that they disagree so strongly that they are implying complete opposition whilst appearing to be polite.
These 4 are said with different emphasis which gives or implies the meaning required. You are quite safe using this phrase in normal speech as it will be accepted as such but you may still get a vehement reply.
- For Teachers