Two London MPs are likely to be front runners to replace Jeremy Corbyn as Labour leader.
Shadow Foreign Secretary Emily Thornberry and Shadow Brexit Secretary Sir Keir Starmer are tipped to enter the leadership contest.
The Tory landslide prompted Jeremy Corbyn to announce he will not lead Labour into another election after his party suffered humiliation.
Jon Lansman, founder of Corbyn backing campaign group Momentum said he expected Mr Corbyn to resign.
Ms Thornberry, who hopes to be re-elected in Islington South, backed remain in the 2016 EU referendum.
She has deputised for Mr Corbyn at Prime Minister's Questions and was also involved in despatch box clashes with Boris Johnson when he was Foreign Secretary.
Sir Keir, a former Director of Public Prosecutions, is standing in Holborn & St Pancras. He was first elected as an MP in 2015.