In the Fourth Anglo-Mysore War in 1798–99, he betrayed Tipu Sultan during the Siege of Srirangapatana, paving the way for a British victory. During the siege, although the invading English troops were starving, Sadiq withdrew his troops, allowing the British to commence their attack on the fort.^[2] He betrayed Tipu, killing Tipu loyalist Ghazi Khan and later arranged to have Tipu trapped behind locked doors.^[3] Sadiq was killed by some of the dismayed Mysorean troops immediately following the defeat as he attempted to go over to welcome the British.^[4]

Following his death, Sadiq's body was mutilated, exhumed and defiled for over two weeks by the angered general public, including women and children, dismayed at his betrayal of Tipu Sultan,^{[citation needed]} forcing the administration to impose "strong measures". Even today, tourists pelt the spot where Mir Sadiq was killed. ^{[5][page needed]}

Mir Sadiq's mausoleum, also located in Srirangapatna, has regularly been assaulted by shoes thrown by visitors over the years.^[6][7] Presently, it is in a severe state of disrepair, rarely visited, ^[8] and its lands have been encroached. ^[9]

Muhammad Iqbal, the notable poet of Indian subcontinent, had condemned Mir Jafar and Mir Sadiq as follows:^[10][1]

جافر از بنگال، و صادق از دکن
ننگِ آدم، ننگِ دین، ننگِ وطن

Translation:

Jafar of Bengal and Sadiq of the Deccan:
A stigma on humanity, on religion, and the country.

• Mir Jafar