OTTAWA (Reuters) - Canada will change how it counts non-permanent residents, the main statistics agency said on Thursday, after an economist said the current methodology may have overlooked about a million foreign students, workers and others.

The decision comes amid a fierce debate on a housing affordability crisis, which has been blamed on an increase in migrants and international students, fueling demand for homes just as rising costs have slowed construction.

The government, under growing political pressure, has said it could consider capping foreign student visas.

In a note on Wednesday, CIBC Capital Markets economist Benjamin Tal said the argument for any such limits would be even more pressing if the government had the real figures.

Statistics Canada said it stood by its figures, but added that it will publish new, more detailed data on non-permanent residents next month using a revised methodology.

"We constantly evaluate and review our methodology to consider emerging demographic trends and new data needs," Statscan said in an emailed statement. Statscan's terminology for non-permanent residents covers people living in Canada with work or study permits and asylum seekers.

Tal said Statscan's new approach would help to give a better sense of the actual numbers in the country.

"A precondition for any policy in general, and housing policy in particular, is to know the size, the magnitude of the shortage," Tal said in a phone interview on Thursday.

(Reporting by Ismail Shakil in Ottawa; Editing by Andrew Heavens)