ABC radio staff have been instructed to tackle unconscious bias about who they put on air by throwing out "old ideas and assumptions about the average Aussie" and making sure their election broadcasts contain a "healthy mix of ethnicities and accents".

The advice, in an email to staff by ABC head of radio Michael Mason, came just hours after new Managing Director Michelle Guthrie used her first official day in the job to say boosting diversity at the public broadcaster would be one of her top priorities.

Ms Guthrie's predecessor Mark Scott and said one of his regrets from his 10 years in the job was that the ABC still did not reflect the ethnic diversity of modern Australia and women were under-represented on air.