The former air chief has quit from the Institute of Defence Studies and Analyses (IDSA) and it is learnt that it has been accepted by Antony, sources in the IDSA said.
The resignation has come after Tyagi was given indications by the government that it would be not be proper for him to continue in office till the probe is completed in the alleged scam, they said.
The investigations in the scam are still going on in India and trials in the case are expected to begin in Italy today.
The Italian authorities have also named alleged middlemen including Guido Haschke and Christian Michael for paying bribes to their Indian agents.
More From This Section
The CBI in India is also investigating the case and has questioned Tyagi and his three cousins for their alleged role in the deal.
A number of companies based in India, Mauritius and Tunisia have also been named by the investigation report for having been allegedly used by the middlemen to route their bribes to Indian agents.
Antony took a firm stand on the issue and suspended the payments to the Anglo-Italian firm and put on hold the delivery of any more choppers pending inquiry in the case.