Labor has claimed the seat of Corangamite in south-west Victoria with Liberal incumbent Sarah Henderson's hopes of a late surge in postal votes drying up.

Ms Henderson conceded the seat on Wednesday night.

"In Corangamite, with postal voting counting now well under way, it has become clear that I will not be able to close the margin necessary to retain the seat," Ms Henderson said.

She congratulated Labor's Libby Coker on her victory.