The phrase “No Taxation Without Representation!” was coined by Reverend Jonathan Mayhew in a sermon in Boston in 1750. By 1765 the term “no taxation without representation” was in use in Boston, but no one is sure who first used it. Boston politician James Otis was most famously associated with the phrase, “taxation without representation is tyranny.”
Parliament had controlled colonial trade and taxed imports and exports since 1660. By the 1760s the Americans were being deprived of a historic right.The English Bill of Rights 1689 had forbidden the imposition of taxes without the consent of Parliament. Since the colonists had no representation in Parliament the taxes violated the guaranteed Rights of Englishmen. Parliament contended that the colonists had virtual representation. (from wikipedia)