In 1766 Allsopp was appointed as deputy provincial secretary and assistant clerk for the Council of Quebec and provincial enrolments. Murray refused to recognise the appointments but was recalled to England in June. Guy Carleton was appointed as lieutenant governor of the province and Allsopp assumed his appointed roles. His job included issuing annual licences for taverns and fur-traders. In 1766 he started a company with two other businessmen, John Welles and Samuel Jacobs, to manage a potash works in
Lower Town. He began an association with Olive, Watson and Rashleigh sometime around 1767 and became their central agent in Quebec. In 1769 he was appointed deputy commissary general, which involved allocating provisions to outposts across Quebec. The potash works failed in 1772, and in 1773 he bought adjacent
seigneuries with his brother-in-law John Bondfield, which included a gristmill. Two years later Allsopp bought Bondfield's land and continued operating the gristmill, which caused Allsopp to become indebted to his grain suppliers. Allsopp was the commissary general during the
1775 American invasion of Quebec and that year was appointed to Quebec's Legislative Council. Nevertheless, government officials began to question Allsopp's loyalty to Britain, citing Allsopp's criticism of the
Quebec Act. He was removed from his government positions in 1777 and publicly assaulted in 1778 while accused of being a rebel. In 1778 Allsopp increased the amount of debt he owed by building a gristmill on the
Jacques-Cartier River, which was coupled with debts from wartime trade restrictions, and conflicts with other merchants. In 1784 he travelled to London to negotiate a financial settlement for his firm and speak with politicians about his dismissal from the Quebec Legislative Council, reforms to the Quebec judicial system, and appealing the
Quebec Act. In 1783, all interest on his debts was cancelled by the
King in Council. Allsopp returned to Quebec in 1785 and continued to advocate for reforms to the judicial system. In 1787, he participated in an investigation into the Quebec justice system and criticised its inconsistency. He continued expanding his business and in 1788 his milling complex was the province's largest producer of flour. He was also a leading figure in advocating for a representative assembly and the adoption of English commercial law, and in 1789 advocated for a trade agreement with the
British West Indies. When the
Constitutional Act of 1791 was adopted, which split Quebec into two provinces, Allsopp claimed that he was to be credited for its passage. In 1792 he lost the election to represent Upper Town Quebec in the province's legislative assembly, and his appointment to the legislative and executive councils was rejected by Home secretary
William Wyndham Grenville. He withdrew from provincial politics at this time and rarely commented on provincial affairs in the 1790s. In 1793 a fire destroyed his main gristmill, and a second mill was destroyed in 1796. The mills were rebuilt and operational shortly afterwards, and a third mill was added to the complex. In 1799 he was appointed as a Quebec
justice of the peace. ==Personal life and death==