Foreign Secretary S Jaishankar summoned Pakistan High Commissioner to India Abdul Basit and gave a strongly-worded demarche, which said the proceedings that have led to the sentence against Jadhav were "farcical" as there were no "credible evidence" against him.
"We have seen the ISPR press release today regarding Shri Kulbhushan Jadhav, an Indian citizen, who has been awarded a death sentence by a Pakistani military court martial," the demarche said.
"Shri Jadhav was kidnapped last year from Iran and his subsequent presence in Pakistan has never been explained credibly. The Government of India, through its High Commission in Islamabad, has repeatedly sought consular access to him, as provided for by international law. Requests to that effect were formally made 13 times between 25 March 2016 and 31 March 2017. This was not permitted by the Pakistani authorities," the statement said.
"The proceedings that have led to the sentence against Shri Jadhav are farcical in the absence of any credible evidence against him. It is significant that our High Commission was not even informed that Shri Jadhav was being brought to trial. Senior Pakistani figures have themselves cast doubt about the adequacy of evidence. The claim in the ISPR release that Shri Jadhav was provided with a defending officer during the so-called trial is clearly absurd in the circumstances.
"If this sentence against an Indian citizen, awarded without observing basic norms of law and justice, is carried out, the Government and people of India will regard it as a case of premeditated murder," the foreign secretary said in the demarche.
Pakistani military said Jadhav was sentenced to death for 'waging war' against Pakistan.
Kulbhushan Jadhav was given the death sentence by the Pakistan Military, Inter-Services Public Relations (ISPR), Pakistan said in a statement on Monday.
Jadhav was arrested on March 3, 2016 through an operation in Balochistan's Mashkel area for his alleged involvement in espionage and sabotage activities against Pakistan, the ISPR said.
"The spy was tried through Field General Court Martial (FGCM) under the Pakistan Army Act (PAA) and awarded the death sentence. Today Chief of Army Staff Gen Qamar Javed Bajwa confirmed his death sentence awarded by FGCM," the ISPR said.
Jadhav was "tried by FGCM under section 59 of Pakistan Army Act (PAA) 1952 and Section 3 of official Secret Act of 1923," ISPR said.
Jadhav "confessed before a magistrate and court that he was tasked by Indian spy agency Research and Analysis wing to plan, coordinate and organise espionage and sabotage activities seeking to destabilise and wage war against Pakistan through impeding the efforts of law enforcement agencies for the restoration of peace in Balochistan and Karachi," the ISPR said.
The accused had been "provided with a defending officer as per legal provisions," the ISPR said.
India has acknowledged Jadhav as a retired Indian Navy officer, but denied the allegation that he was in any way connected to the government.
Kulbhushan used to run a business in the Iranian port city of Chabahar
Earlier in March 2016, the Ministry of External Affairs said that the former Indian naval officer was arrested by Pakistan for allegedly engaging in subversive activities was possibly kidnapped from Iran and denied any possibilities of him being involved in subversive activities in Pakistan.
'Kulbhushan Yadav', the accused, used to run a business in the Iranian port city of Chabahar. He was seen in a video confessing that he was an official of the Research and Analysis Wing (RAW), India's external intelligence agency.
"The government categorically rejects allegations that this individual was involved in subversive activities in Pakistan at our behest. Our enquiries reveal that he apparently was being harassed while operating a legitimate business from Iran. While we probe this aspect further, his presence now in Pakistan raises questions, including the possibility of his abduction from Iran," the ministry had said.
(With inputs from agencies)