The 1763 to 1765 Grenville ministry began by instructing the Royal Navy to clamp down on smuggled goods and enforce customs duties levied in American ports. The most important was the 1733 Molasses Act; routinely ignored prior to 1763, it had a significant economic impact since 85% of New England rum exports were manufactured from imported molasses. These measures were followed by the Sugar Act and Stamp Act, which imposed additional taxes on the colonies to pay for defending the western frontier. In July 1765, the Whigs formed the First Rockingham ministry, which repealed the Stamp Act and reduced tax on foreign molasses to help the New England economy, but re-asserted Parliamentary authority in the Declaratory Act.