Four years later, he helped found another St. Patrick's church, this time in York. In 1814, Egan (now bishop of Philadelphia) promoted de Barth to the position of Vicar General. Egan died shortly thereafter. Until a suitable bishop could be found, Carroll, now Archbishop of Baltimore, appointed de Barth as the apostolic administrator. De Barth tried to refuse this assignment, likely due to the ongoing disputes in Philadelphia between the clergy and the lay trustees of the city's parishes over who should control the churches, but he eventually accepted and took temporary control of the diocese. He spent little time in the city, leaving day-to-day control of the parishes there to Terrence McGill, a local priest. Carroll considered requesting de Barth's appointment as bishop, but decided against it because of de Barth's lack of theological study and reputation for having a quick temper. Carroll died in 1815, and his successor, Leonard Neale, offered de Barth the position of bishop, but de Barth declined it. In a letter to Neale, de Barth wrote that if you do not forward my objections [to the appointment] to the Holy See ... I will not accept, but will kneel down and devoutly put the bulls in the fire ... and then farewell, Monseigneur. Neither you nor anyone else shall ever know the corner of the globe where I shall vegetate the few years still left to me to live. Neale accepted de Barth's refusal, and the see remained vacant. In 1817, after Neale died, de Barth traveled to Baltimore to participate in the episcopal consecration of Neale's successor, Ambrose Maréchal. Because he expected the appointment of a new bishop soon, de Barth hesitated to take any drastic actions as administrator. As such, he spent much of his time in the city and, as historian Joseph L.J. Kirlin wrote in 1909, discipline "became more and more relaxed." The ongoing dispute between the lay trustees of St. Mary's Church and the church hierarchy grew more rancorous when de Barth assigned a new priest, William Hogan, to the diocese in 1820. Hogan instantly took the side of the trustees against de Barth; Hogan's unusual behavior would eventually cause his excommunication, but not until de Barth's tenure as apostolic administrator had ended. After a vacancy of five years, the see of Philadelphia found a new bishop in Henry Conwell, an Irish-born priest who was installed in 1819 and arrived the next year, freeing de Barth to return to Conewago.