The break-up of the centralised Mughal empire by 1750, led to the creation of numerous semi-independent kingdoms (all provinces of the former Mughal empire). Nawab Siraj ud-Daulah was defeated by the British forces of Sir Robert Clive in the Battle of Plassey in 1757. Thereafter the Nawab of Bengal became a "puppet ruler" depending on military support from British East India company to secure their throne. Siraj-ud-Daulah was replaced by Mir Jaffer. He was personally led to the throne by Robert Clive, after triumph of the British in the battle. He briefly tried to re-assert his power by allying with the Dutch, but this plan was ended by the Battle of Chinsurah. After the defeat at Battle of Buxar and grant of the Diwani (revenue collection) of Bengal by the then Mughal Emperor Shah Alam II, to the British East India Company in August 1765 and the appointment of Warren Hastings by the East India Company as their first Governor General of Bengal in 1773, the Nawabs authority became restricted. By 1773, British East India company asserted much authority and formed the Bengal Presidency over areas ruled by the Nawabs i.e. the Bengal subah, along with some other regions and abolished the system of Dual Government. In 1793 (during Nawab Mubarak ud-Daulah's reign), the Nizamat (military power, civil and criminal justice) was abolished, British East India company thus annexed this former Mughal province as part of their empire and took complete control of the region, and the Nawabs of Bengal became mere pensioners of the British East India Company. All the Diwan offices except the Diwan Ton were also abolished.

Answer this question: who abolished the dual government system in bengal? Let's think fast. Stream of consciousness:
To answer the above question, the relevant sentence is: By 1773, British East India company asserted much authority and formed the Bengal Presidency over areas ruled by the Nawabs i.e. the Bengal subah, along with some other regions and abolished the system of Dual Government. So the final answer is British East India.