The mining union is piling pressure on the Allan government to explain how it will guarantee energy security for Victorians after the huge Yallourn coal power station closes as delays to transmission and offshore wind projects raise fresh doubts about renewable replacements.

The slow development of gas options to replace declining output from the Bass Strait fields has added to anxiety among industry and labour unions about secure power when EnergyAustralia closes the 1480-megawatt Yallourn generator in mid-2028.