Treasurer Scott Morrison has savaged Bill Shorten's leadership after a peak small business body threw its support behind the Greens over Labor.

Mr Morrison jumped on the declaration from the Council of Small Business Organisations that the opposition's stance on business has regressed under Mr Shorten, vouching for the minor party instead.

It was a "bizarre position", the treasurer said.

"For goodness sake, where has Bill Shorten taken the Labor party ... that the Greens are even seen as a more credible economic managers," he told Sky News on Friday.

The council will launch a mail campaign in the Labor-held Melbourne seat of Batman - as well as eight other marginals - highlighting the opposition's anti-business stance.

"The Greens are more small business-friendly. We just don't know what has happened. Labor has regressed," chief executive Peter Strong told The Australian.