The European Court of Justice (ECJ) has ruled that current UK maternity pay policy is unlawful:
In the UK statutory maternity pay (SMP) is calculated on the basis of a worker's average weekly pay during the eight week period before SMP starts
ECJ's view is that if a pay rise takes effect during this eight-week period or during the 26 week SMP period itself the SMP must be re-calculated to reflect the rise and employees may be able to bring backdated claims.
Acorn's tip: make sure any pay rises that take effect after the start of the statutory maternity leave are factored into SMP.