Shadow home secretary Diane Abbott is visiting the controversial Yarl's Wood Immigration Removal Centre amid reported concerns over the treatment of women detainees.
Her arrival at the centre in Bedfordshire coincided with reports of a hunger strike by more than 100 women held there.
The women were said to be protesting at their "offensive" treatment by the Home Office.
One Algerian woman told The Independent that she felt "broken down" by her time there.
"Every day I wake up and I have to think of a reason to go on. I have given up thinking about the outside," she was quoted as saying.
"I feel like I am in someone's dungeon and no one is letting me out."
Ms Abbott has been seeking access to the facility, which is run by Serco, for more than a year.