Shiv Shankar Menon, India's foreign secretary, has said that Pakistan's spy agency was linked to planners behind the Mumbai attacks.
The statement, delivered at a foreign-affairs conference in Paris, is the first by an Indian official directly linking the Pakistani agency to the attacks last November.
"The perpetrators planned, trained and launched their attacks from Pakistan, and the organisers were and remain clients and creations of the ISI (Inter Services Intelligence)," Menon said.
His speech was delivered on Wednesday but a transcript was released by India's foreign ministry on Thursday.
The co-ordinated attacks by armed men on several locations across India's financial capital left at least 170 people dead and hundreds wounded.
The attacks also strained relations between New Delhi and Islamabad.
In his speech, Menon also accused Pakistan of "prevarication" in investigating the attacks and bringing the perpetrators to justice.
Al Jazeera's Matt McClure, reporting from New Delhi, emphasised the significance of Menon's speech.
"Certainly there have been reports in the Indian media ... that have pointed the finger that some of these young fighters were infact trained in Pakistan by former members of the military.
"But this is the first time, that we know of, that the government directly pointed the finger, not just at Pakistan but at a Pakistan government organisation".
India accuses the Pakistan-based Lashkar-e-Taiba (LeT) group for the attacks.
New Delhi has provided Islamabad with a dossier, reportedly containing proof of Pakistani links to the attacks. Indian officials say Pakistan has still not responded to the evidences provided.