 Downing was returned for Morpeth in the Convention Parliament of April 1660, a constituency that he represented in every ensuing parliament till his death, and he spoke with ability on financial and commercial questions.In 1665, after his expulsion from the Netherlands and as a member of parliament, Downing attached a clause to a bill to fund the war's continuation that specified that the money could only be used for the war effort.This previously little-used move, opposed strongly by Lord Clarendon as an encroachment on the royal prerogative, effectively made permanent the parliamentary appropriation of supplies (meaning that Parliament gained the right to specify that tax revenues should be used only for a particular purpose, rather than spent as the King's government saw fit).