The glass items were spotted behind a counter in a central London branch.
Packaging makes clear the pipes are ‘for tobacco use only’.
But the shape and design are often associated with using illegal substances.
The pipes were sold alongside vapes in Farringdon.
Stunned shopper Frank Bolt said: “I only popped in to the Post Office for some stamps and was confronted by a crack pipe. I couldn’t believe my eyes.
“When I asked staff what they were doing they shrugged and looked a little sheepish.
“Drug addicts must be delighted at having the pipes on hand next to the passport applications.
“I know the Post Office brags about serving its local community but this is ridiculous.”
A Post Office spokesperson said: “A Postmaster often has a retail area in addition to their Post Office and they decide what to sell.
“It is not illegal to sell, buy or to possess unused glass pipes.
“They can be purchased in shops and online including Amazon. The packaging clearly states that it is for tobacco use only.”
But later, a Post Office spokesperson added: “The Postmaster has also agreed to remove the stock of glass pipes.”