A report condemning Southland to less than 1 per cent economic growth a year for the next 20 years has been slammed by Venture Southland and the Southland Chamber of Commerce.

The Institute of Economic Research study has forecast Southland growth until 2021 as the lowest of any region in New Zealand at just 0.62 per cent a year.

Venture Southland strategy marketing manager John Grant yesterday lashed out at the report, which he said was based on data that was no longer relevant to Southland.

Chamber of Commerce chief executive Richard Hay agreed, saying the report was most likely compiled by a "statistician in Wellington who didn't know what was going on in the powerhouse of New Zealand".