Lady Gaga has won an injunction stopping the makers of an online children's game promoting an animated character called Lady Goo Goo.
The character features on popular children's website Moshi Monsters, which allows children to adopt a virtual pet monster.
The sunglasses-wearing, blonde baby became an internet hit with the release of her music video The Moshi Dance on YouTube in June.
It drew around one million views per month and Mind Candy, the British company behind the site, wanted to release the single and later an album via iTunes.
But Gaga's lawyers went to the High Court to block the move and have this week been granted an injunction.
They are believed to have submitted evidence which showed some people had been confused about a possible connection to the star.
The injunction bans Mind Candy from "promoting, advertising, selling, distributing or otherwise making available to the public" any work involving Lady Goo Goo.
Mind Candy founder Michael Acton Smith said: "The ruling could set a dangerous precedent in trademark law impacting tribute bands and parody songs."
He added that it was a "huge disappointment" because it was "obvious" children could differentiate between the character and the American singer.
"The shame is that millions of kids fell in love with Lady Goo Goo's debut single on YouTube and now won't be able to enjoy her musical exploits.
"It was all done in the name of fun and we would have thought that Lady Gaga could have seen the humour behind this parody."
With over 50 million registered users worldwide, Moshi Monsters has a huge global community of children aged six to 12 and is dubbed "Facebook for kids".
Children visiting the website can adopt and care for a pet monster, and solve puzzles earning them reward points called rox.
Rox can be used as currency to buy items for the child's adopted monster, such as clothing, food and decorations for the monster's home.
The ruling could lead to other claims because Lady Goo Goo is one of various "moshlings" - or characters - which include Dustbin Beaver based on Justin Bieber.
However, Oliver Smith, an intellectual property lawyer with Keystone Law, said the judgment was unlikely to set a precedent as it was only a temporary injunction.
He said: "The issue is whether the song name Lady Goo Goo is really another Moshi Monster trademark in disguise, looking to piggyback on the success of Lady Gaga.
"English trademark law allows parody songs and tribute bands but not if the names are too similar and one takes unfair advantage of the other's goodwill."