Doubts have been cast over whether the Manchester Gorton by-election can go ahead following the prime minister's decision to call a general election.
Manchester's returning officer is seeking clarification following Theresa May's announcement.
The poll was due 4 May - the day after parliament is set to be dissolved.
This would potentially create the anomaly of a newly-elected MP without a parliament to sit in.
Returning Officer for Manchester Joanne Roney OBE said: "We are seeking advice in discussion with the Government and Electoral Commission and will confirm arrangements for the Manchester Gorton constituency as soon as possible."
The Electoral Commission said the general election decision would not affect the metro mayor elections in Liverpool City Region and Greater Manchester on 4 May as these dates were "set in law".
But the BBC understands the snap poll means the Gorton by-election is unlikely to take place.
Cabinet member David Davis, Secretary of State for Exiting the European Union, said on Sky News the by-election would be cancelled, while the Leader of the House David Lidington told the Commons the decision on whether to hold the poll is one for the returning officer in Manchester.
Mr Lidington said parliament was likely to be dissolved on 2 or 3 May.
The House of Commons votes on Wednesday whether to approve the election.
The by-election was caused by the death of long-serving Labour MP Sir Gerald Kaufman in February.