@JimThio not a referendum, but a constitutional amendment, which requires a 2/3
super-majority vote in both houses of congress and ratification by at least 3/4 of state legislatures.
The election may be held at an earlier date
in the event of an early election motion being passed by a
super-majority of two - thirds
in the
House of Commons, or a
vote of no confidence
in the government which is not followed by a
vote of confidence within 14 days.