Labour leader Jeremy Corbyn's Islington North constituency is one of 50 to be abolished at the next general election, under proposals published by the Boundary Commission for England.
A shake-up of seats in north London would see the constituency Corbyn has represented since 1983 split into two.
Video report by ITV News Deputy Political Editor Chris Ship
Corbyn said he was "very unhappy" about the boundary changes, which could potentially pit him against two of his closest allies - Diane Abbott and Emily Thornberry - in the race for selection as candidates for the new seats of Islington and Finsbury Park & Stoke Newington.
The Labour leader said, however, that he was "very confident" about the future, adding: "I look forward to representing some parts of Islington."
Under the proposals, Corbyn's leadership rival Owen Smith would see his Pontypridd seat merged with the neighbouring Cynon Valley constituency of veteran backbencher Ann Clwyd.
Chuka Umunna (Streatham), Yvette Cooper (Normanton, Pontefract and Castleford) and Tristram Hunt (Stoke-on-Trent Central), are among leading moderates facing significant changes which could leave them vulnerable to de-selection attempts by hardline Corbyn supporters.
Other plans include:
Number of MPs in the House of Commons to be reduced from 650 to 600
This reduction would save taxpayers £66 million over five years
MPs in England to be cut from 533 to 501, in Scotland from 59 to 43
MPs in Wales to be cut from 40 to 29, in Northern Ireland from 18 to 17
The move is expected to hit Labour the hardest, with more constituencies abolished or merged in strongholds such as London, Wales, the North-East and North-West than in the Conservative-dominated shires.
Theresa May's Maidenhead seat remains unchanged, while Chancellor Philip Hammond's Runnymede and Weybridge seat also largely stays the same.
Foreign Secretary Boris Johnson (Uxbridge and South Ruislip) faces a significant redrawing of the electoral map, but appears well-placed to secure the Conservative nomination for the new seat of Hillingdon and Uxbridge.
Former chancellor George Osborne's Tatton seat in Cheshire is set to be abolished.
Labour suggested that it would fight the "unfair, undemocratic and unacceptable" changes, saying that they are based on an outdated 2015 version of the electoral register with almost two million voters missing.
Constitutional changes should be done fairly and consensually, to ensure that everyone given a voice.
Constitution minister Chris Skidmore said the government was "committed to ensuring fair and equal representation for the voting public across the UK is in place by the next general election".