Michael Martin has told MPs he will resign as Speaker of the House of Commons on 21 June, following the row over MPs' expenses.
In a terse statement lasting only 35 seconds, he said that his decision was so that "unity can be maintained". Mr Martin will also stand down as an MP, prompting a by-election in his Glasgow North East seat.
He is the first Speaker in more than 300 years to be forced out of his job.
Nick Robinson reports.