The New Zealand Transport Agency has denied Rotorua's wish to welcome visitors in Te Reo instead of English.
Rotorua Lakes Council proposed an entry sign welcoming people to the city reading 'Haere Mai Ki Rotorua' (Welcome to Rotorua), declaring it 'New Zealand's first bilingual city'.
However, NZTA says under a 2004 rule the sign must be written in English.
"The only wording acceptable on these signs is 'Welcome to [locality]."
Associate Transport and Regional Development Minister Shane Jones told the Sunday Star-Times the ruling is "really odd".
"Rotorua after all is a cultural destination and there is no culture without the Māori in Rotorua.
"If they can't have Te Reo, do they want the Rotorua Māori to take up finger language? And I don't mean sign language by that either."
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Rotorua mayor Steve Chadwick says she's going to fight the ruling.
"We're going to challenge that, change the rules.
"It's very sad that you can only say 'Welcome to Rotorua', this may be the first challenge to demonstrate te reo is an official language."
The NZTA told the Sunday Star-Times it will work with local councils to "safely incorporate bilingual road signage".
"We're keen to help Rotorua District Council develop an entrance sign which fits in with their work to promote Rotorua as a bilingual city, while still functioning as an effective traffic safety device."