Software billionaire Mike Cannon-Brookes is ramping up his push to have all four of his director picks for AGL Energy voted onto the board, telling shareholders the existing board is “not up to the challenge of delivering on AGL’s potential”.

In a letter to be sent on Monday to investors in the embattled electricity supply giant, the Atlassian co-founder and AGL’s biggest shareholder urges fellow investors to “use your power” and vote for renewal of the board at the annual general meeting on November 15.