There was already growing opposition to the Labour Government, from both the Conservatives and the Liberals, over the treaties it had signed with the Soviet Union in August.
In the event, it was the Campbell Case which brought them down.
On the 1 October the Conservatives put forward a motion of censure against the Government over its handling of the case.
On the 2 October the Liberals put forward an amendment to this motion, calling for an Inquiry by a Select Committee.
Ramsay MacDonald decided to treat it as a vote of confidence. If either motion were carried he would ask for the dissolution of Parliament.
At the debate on the 8 October, the Conservative Leader Stanley Baldwin announced that his party would vote against their own motion and for the Liberal amendment. This ensured the Liberal amendment was carried.
The following day Ramsay MacDonald went to see the King and Parliament was dissolved.