Welsh Assembly Member Eleanor Burnham has apologised for referring to the Japanese as "Japs" in a chamber debate.
The Liberal Democrat AM for north Wales made the comment while talking about Japanese trains.
After criticism by other AMs she denied intending any slur, adding: "I had no intention in mind. I do apologise."
Presiding Officer Dafydd Elis-Thomas said: "We should use full and proper terms for all nationalities so there is no implied insensitivity.
"We would not want to be called Butts, Taffs or Welshies," he added.
Carl Sargeant, Labour AM for Alyn and Deeside, called for her to be removed from the Lib Dems' regional list of assembly election candidates.
The row flared after Mrs Burnham told fellow AMs: "Why not invest in the Maglev train that the Japs use to whizz through the countryside at about 320mph, rather than piddling around at 60mph as we do?"
On Wednesday, she said: "I certainly had no intention to have any slur on the Japanese.
"I was in fact eulogising about their wonderful train system."
She said Britons were sometimes called "Brits".
Mr Sargeant said: "This was appalling behaviour from the Liberal Democrat AM for north Wales, especially coming hot on the heels of the Big Brother racism scandal.
"The Liberal Democrat leader in the assembly Mike German should take the action Channel 4 executives were too scared to take.
"He should immediately remove Eleanor Burnham from the north Wales regional list for this year's election."