A breastfeeding mother was left embarrassed and upset after a male staff member walked in on her using the bathroom to pump her breast milk, and then stayed to lecture her.

Sophia McBain wrote on Twitter that she was traveling without her baby and needed to “express milk” while she was at the Heathrow Airport. The mom said she asked staff where she could pump in private and they instructed her to use the baby changing room.

“I used it, feeling a bit bad to be occupying the room for 20 minutes but I was really uncomfortable and needed to do this,” McBain tweeted out on Sunday.

While in the stall, McBain didn’t hear someone knock. She believes that prompted the person to get a staff member to come open the door.

“A male attendant came, unlocked the door and while I was still attached to a machine with my breasts out,” she wrote.

“[The male attendant] lectured me about how I should leave the door unlocked or pump outside,” she continued. “I felt so exposed and embarrassed. Could a female staff member not be sent? Could he not wait until I was unplugged and dressed? Can breastfeeding women not have a room to pump undisturbed & in private?”

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McBain contacted Heathrow Airport about the situation, but received an unsatisfying response.

“I told people yesterday that I wasn’t so upset about my horrible experience @HeathrowAirport, I just didn’t want other women to go through the same. But then I received this excuse-filled, non-apology to my formal complaint & I am so sad,” she tweeted.

McBain tweeted out the response she received, which defended having a male bathroom attendant enter the restroom and said “…if he had not heard any response from requests to enter he would of [sic] thought that someone might have this from the outside as a prank.”

“In this, while it was uncomfortable it was not entirely his fault for entering after warning,” the “non-apology” continues.

At the end, the Heathrow Airport employee tells McBain that her “feedback” was passed along to the terminal’s manager.

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The unsatisfactory response prompted McBain to illustrate just why this matter was so important in a series of tweets.

“To explain why I was upset I compared it to someone bursting in on your while you are on the toilet and then calmly telling you, while your pants are still round your ankles, that you are hogging the public bathroom,” she tweeted.

“Also, sticking your breasts into an electric breast pump is so undignified looking I don’t even like it when my husband sees me doing it. Why would I want strangers to see this?” she continued.

“I didn’t explain that my right side, which I didn’t pump because I was too embarrassed and stressed, was so painful five hours into my flight that I cried with relief when the @BritishAirways cabin crew said I could use their rest area to pump,” McBain added.

“But I did explain that it’s not just that breastfeeding women feel uncomfortable when they can’t pump — it puts us at risk of a painful and potentially serious condition called mastitis," she tweeted.

"I also did not explain that this kind of s— is why the U.K. has the lowest breastfeeding rate in the world,” she wrote.

Because of her experience, McBain is setting out to change the way Heathrow Airport handles breast pumping mothers. McBain has already reached out on Twitter to cleaning supplies company, Seventh Generation, who has started a campaign to create private rooms for women to pump in at John F. Kennedy Airport in New York City.

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“I made clear I didn’t want to get anyone into trouble, this wasn’t about one staff member. It’s a systemic problem,” she said. “No thought has been given to breastfeeding travelers, we have no space to pump/breastfeed in private and staff have clearly received no training.”

Since sharing her story, Heathrow Airport was reached out with another apology to McBain, and promised to “look to provide an additional private and comfortable area for passengers to express milk and nurse infants in addition to our current baby-change facilities.”