VATICAN CITY – The Vatican on Wednesday urged a breakaway Catholic ​group dedicated to the old Latin mass to cancel plans to ordain new ‌bishops without consent from Pope Leo, warning the action would incur excommunication from the 1.4-billion-member Church.

In the first known threat of the Church’s most severe penalty during Leo’s papacy, the Vatican’s doctrinal office told the Swiss-based Society ​of St. Pius X any ordination of bishops would create a “schism”, or formal rupture ​with the pope.

The planned ordination ceremony would mark “a grave offence against God ⁠and entail the excommunication established by the Church,” Cardinal Victor Fernandez, head of the office, ​said in a statement.

The Society of St. Pius X is an ultra-traditionalist group that denies the ​key teachings of the Second Vatican Council, a landmark Vatican gathering of bishops in the 1960s that pursued a range of reforms for the global Church.

The Council also allowed for the Mass, until then said only ​in Latin, to be celebrated in local languages.

The society rejected that change, citing a ​desire for the Latin rite’s sense of mystery and formality.

Excommunicated persons are considered completely separated from the Church. ‌

They ⁠are unable to receive sacraments or hold a church office until they repent.

If they die while excommunicated, they are unable to receive a Catholic burial.

The Society of St. Pius X, which says it counts 733 priests worldwide, has had tense relations with the Vatican for decades.

Its late founder, Archbishop ​Marcel Lefebvre, was excommunicated ​in 1988 after ⁠ordaining four bishops without permission from then-Pope John Paul II.

Benedict XVI, John Paul’s successor, sought to renew dialogue with society and lifted four ​remaining excommunications.

The current leadership announced in February that it planned to ​ordain new bishops, ⁠without Vatican approval, in July, citing a need for more prelates to lead the society.

It is a strict teaching of the Church that only the pope can authorize the consecration of new ⁠bishops, in ​order to maintain the Church’s ties to Jesus’ 12 ​apostles, who are considered the first priests and bishops.

Consecration without papal consent incurs automatic excommunication for both the person being ​consecrated and the bishop conducting the ceremony.