They will be trying to win fellow housemates' approval by preparing a speech on their contribution to the series.
Louise Cliffe, Alex Rose, Tom O'Connell, Jay Mckray and Aaron Allard-Morgan will each put together a five-minute presentation emphasising why they should win the competition.
Dressed in suits, video profiles of the remaining housemates will appear on the plasma screen.
Big Brother will then ask the contestants to declare their votes through a special ballot box.
The 'Housemate's Housemate' will be awarded a bottle of champagne and a winner's sash ahead of this Friday's grand final.
Big Brother continues tonight at 10pm on Channel 5, while these scenes will be shown on Thursday night.
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Watch Big Brother reveal the 'Housemate's Housemate' task below: