The New York singer's lawyers have given the manufacturers until 1600 GMT Wednesday to change the name "if you wish to avoid proceedings for trade mark infringement and passing off", according to a letter addressed to London restaurant The Icecreamists Limited.
The cafe in the trendy Covent Garden district must also "cease and desist from in any other way associating with Lady Gaga any ice cream you are offering," said the letter from law firm Mishcon de Reya.
The letter accuses The Icecreamists of "taking unfair advantage of, and riding on the coattails of" Lady Gaga's trademarks in a manner that is "deliberately provocative and, to many people, nausea-inducing".
The ice cream has proved a big hit, with the first batch sold out within days of going on sale. It is made with milk expressed by 15 women who replied to an advertisement posted on an online mothers' forum.
Each serving costs £14 and is brought out by waitresses wearing flamboyant costumes, something Lady Gaga is well-known for.
But it is now off the menu after Westminster City Council, the local authority, seized the ice cream for health and safety checks.
"We are taking the ice cream away for samples," a spokeswoman told AFP, adding that they expected the results on Monday.
"It's not a ban. The owner has voluntarily agreed not to make any more or sell any more until we've got all the results."
Breast milk could carry viral infections, including hepatitis, she explained.
The manufacturers have said they use the same screening procedures as blood donation centres or milk banks in London.
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