Census data about languages spoken in Manchester is "way out", according to a University of Manchester professor.
The data released on Wednesday named about 100 languages in response to the question, 'what is your main language?'
However, Professor Yaron Matras claims the number "significantly under-represented both languages spoken and the numbers who speak them".
He said the university's Multilingual Manchester project had documented "at least 153 languages" in the city.
The data from the 2011 census showed the vast majority of Manchester's residents used English as their main language, but also reported significant numbers using either Urdu, Polish, Arabic, Farsi, Somali, Panjabi or Bengali as their first tongue.
Prof Matras said, while the data had provided "important confirmation of Manchester's enormous linguistic diversity" the research revealed a greater number of languages and people who spoke them.
He said: "Manchester is home to the fourth largest Yiddish-speaking community in the world, yet the census only mentions five speakers.
Romani is reported to have only 29 speakers, yet a recent survey by the [university's] Romani Project confirms that there are several hundred Romani speaking households in the city.
"Only 1,700 people are reported to speak Cantonese, and only 13 are reported to speak Caribbean Creole, but these figures must surely be wrong. Both communities have many thousands of members."
'Lack of clarity'
The professor said the difference in numbers could be down to an "under-reporting" of languages, partly through lack of awareness or "fear of stigmatisation".
It could also be the result of people misunderstanding the census question.
He said: "For many people, English is [their] main [language] because they use it during most hours of the day at work or place of study, but it is not their home language."
He added that he was concerned about the accuracy of the figures for the rest of England and Wales.
He said: "Health services, businesses and schools are increasingly embracing multilingualism to reach their target audiences - having accurate data on the language needs of their communities is an important way to help them."
When asked to respond to Prof Matras's claims, a spokeswoman for the Office for National Statistics said the data published was what had been collected on the census forms for the city.
The Multilingual Manchester project was set up by the university in 2010 to document, protect and support the languages spoken in the city.