An Ash Wednesday service at a Catholic school has left 90 pupils and staff with chemical burns, as parents say they are considering legal action.

Two pupils were hospitalised and scores more were burned after a priest marked crosses on assembly-goers’ foreheads as part of an Ash Wednesday ceremony at a top-performing school.

A total of 73 students, 16 staff and the chair of the governors were burned after being marked with the ash as a token of penitence and mortality during the ritual at the Saint Augustine’s Catholic High School in Worcestershire.

The priest, assisted by two students, began marking pupils’ foreheads. But the ritual was stopped half way through when children complained of 'tingling', Cassena Brown, 39, the mother of a badly-burnt pupil, said.

The cross marking then ceased and students were asked to wash the ashes off immediately to ensure no further discomfort was felt, the school said.