Labour MPs Tristram Hunt and Jamie Reed have formally stood down from the House of Commons, paving the way for by-elections in Stoke-on-Trent Central and Copeland on February 23.
Under arcane rules governing MPs' resignations, Mr Hunt has been appointed Steward of the Chiltern Hundreds and Mr Reed Steward of the Manor of Northstead - Crown appointments which bar their holders from sitting in the Commons.
The pair - both prominent critics of Jeremy Corbyn's leadership - took the unusual step of quitting Parliament to take up outside jobs, in a development widely seen as a sign of Labour's moderate wing losing hope of regaining control over the party in the near future.
Their departure presents Mr Corbyn with a couple of awkward by-elections in what have previously been safe Labour seats.
The party faces a particularly tough challenge in Mr Hunt's former Stoke Central seat, where Ukip leader Paul Nuttall is hoping to capitalise on a strong Brexit vote in last year's EU referendum to secure himself a place in the Commons.
Liberal Democrats announced that their candidate in Stoke Central will be consultant cardiologist and "passionate Remain supporter" Zulfiqar Ali, who said he would fight the campaign on a platform of keeping the UK in the European single market.
Dr Ali stood for the Lib Dems in the constituency in the 2015 general election, taking fifth place as the party saw its vote slump from 22% to 4%.