His remarks came a day after the UK government said it would take "extreme action" if any British citizen was being "tortured".
The case of Scottish-born Jagtar Singh Johal alias Jaggi, who was jailed earlier this month in India, was raised in the House of Commons yesterday following reports of his alleged "torture" in custody.
The chief minister said said due process of the law was being followed in the case.
"The accused was not tortured," Singh said, adding that no unlawful method would be adopted during interrogation.
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Singh said the accused was also provided consular access and "the National Investigation Agency (NIA) was involved in the investigation as this conspiracy has international links".
Johal was among five accused arrested in connection with the targeted killings, including that of RSS leader Jagdish Gagneja. Johal, who got married last month, was apprehended from Jalandhar.
The Punjab Police had earlier claimed that it had "sufficient" evidence to prove the complicity of Johal in the targeted killings.
It had also claimed to have found him to be involved in conspiracy, coordination, funding and arranging of weapons for members of the KLF module busted in connections with the targeted killings.
British MP Martin Docherty-Hughes has been campaigning for Johal's freedom and had also written to Downing Street seeking a meeting for his UK-based family with the prime minister.
Aam Aadmi Party (AAP) leader and MP Bhagwant Mann, AAP MLA Kanwar Sandhu also raised concern over the allegations.
On November 19, Punjabi singer and actor Diljit Dosanjh had tweeted he was sad to hear about the alleged torture.
A campaign titled 'Free Jaggi Now' was also being run on social media.