The Morrison government will appeal to the High Court to overturn a landmark legal decision by the full Federal Court which grants shift workers more sick leave.

Workers at a Cadbury factory last month won the right to be receive 12 hours of pay for every sick day - the same number of hours they were rostered on for each shift, instead of the 7.6 hours per sick day they were being paid by employer Mondelez International.

Sick leave entitlements for workers at a Cadbury factory have sparked a High Court appeal. Credit:Paul Jeffers

Attorney-General and Industrial Relations Minister Christian Porter said the government - which had intervened in the original case - was appealing because the decision had "sparked confusion and uncertainty around the way sick and carers leave entitlements should be calculated".

Mr Porter said the Federal Court ruling had "created significant inequities between employees", while also exposing employers of shift workers to wage bills up to $2 billion higher each year.