Fennell, in a letter to the local organising committee, wrote it was "reasonable to conclude that the current situation poses a serious risk to the Commonwealth Games in 2010."
With a year to go until the October 3-14 Games in New Delhi, Fennell has sought an appointment with Prime Minister Manmohan Singh during next month's CGF assembly to brief him on the delays.
"I feel I must personally brief the Prime Minister of India on the lack of preparations and to seek his input in developing an appropriate recovery plan," Fennell wrote, the Hindustan Times reported.
"The government of India has committed significant resources towards the operational delivery of the Games. It would be irresponsible and negligent of the CGF not to share its concerns openly with the government."
Fennell blamed a lack of co-ordination in the local organising committee, headed by Indian Olympic Association chief Suresh Kalmadi, for the delays in preparing for the Games.
"Our concerns are such that unless there is significant change in the management culture and operation of the organising committee these Games will fail from an operational perspective," he wrote.
"The CGF is extremely worried about the organising committee's ability to deliver the Games to any comparable standard to that of the last two editions of the Games in Manchester (2002) and Melbourne (2006).
"I'm looking forward to some urgent actions in order to bring about the successful celebration of the Games in 2010."
Fennell's remarks follow an Indian government report last month that said work on 14 of the 19 sports venues was running late, while nine transport projects to improve Delhi's congested road network were at a "high risk" of not being completed in time.
The Comptroller and Auditor General report said that the aquatic complex, which should have been 93 percent finished by August, was only 42 per cent complete.
It also said the design of the renovated main stadium was still not finalised.
Fennell's latest remarks were flayed by the treasurer of the organising committee, AK Mattoo, who insisted New Delhi will host a successful Commonwealth Games.
"I am shocked to hear his observation on the committee," Mattoo told reporters. "We are doing our best and I am confident we will host a successful Games.
"Delays do happen, but criticising is not going to get you anywhere. Having said that, I am confident we will sit together and resolve the issue soon."
The Games, the biggest multi-sport event to be staged in India since the Asian Games in 1982, feature 71 nations and territories that comprised the old British empire.
