Jagtar Singh Johal, 39, from Dumbarton, was arrested in 2017, just weeks after his wedding, and has been detained ever since.
Despite being acquitted last year on charges of financially supporting a terror group, he still faces federal charges in India based on the same allegations.
His family and MP are now urging Foreign Secretary Yvette Cooper to secure his release during her current visit to India.
Douglas McAllister, Labour MP for West Dunbartonshire, said: “There can be no higher priority on this trip than securing the freedom of a young British man who has been unjustly imprisoned for almost nine years.
“I have made this case to the Foreign Secretary personally, stressing the need for urgent action.
“It is not enough to raise the case or call for faster progress: following his acquittal in Punjab, all remaining charges against Jagtar Singh Johal should be dropped, so that he can return home to Dumbarton.”
A group of United Nations experts has described Johal’s detention as arbitrary and said he has been subjected to “a form of psychological torture”.
During a recent consular visit, Johal was informed of Cooper’s upcoming trip to Delhi and reportedly told staff: “I’m stuck in a broken country with a broken judicial system.”
His brother, Gurpreet Singh Johal, said the family has repeatedly shared a plan with Cooper to secure his release and hopes this visit will lead to concrete action.
Gurpreet said: “Each time a Foreign Minister travels to India for meetings, a part of me believes that Jagtar will be on the plane home with them.
“We look for tiny signs of progress and reasons to hope and, each time, the disappointment is crushing.
“When I met Yvette Cooper last year, we presented a clear plan to get Jagtar home – this visit is her big chance to put it into action.
“She has all the tools to succeed where seven other foreign secretaries have failed.
“It would be devastating to hear the same weak excuses all over again.”
Cooper is scheduled to meet her Indian counterpart, Subrahmanyam Jaishankar, on Thursday.
The campaign group Reprieve, which has been supporting the Johal family, maintains that there is no legal case against him.
Dan Dolan, deputy chief executive of Reprieve, said: “An Indian court last year acquitted Jagtar on all charges, for lack of evidence, but he remains detained due to eight zombie cases based on the same allegation and the same torture confession.
“This kind of double jeopardy is prohibited in India’s constitution and international law.
“As UN legal experts recently communicated to the Indian authorities, the only just resolution is for the charges to be dropped and Jagtar released immediately.
“It’s past time for the Foreign Secretary to negotiate with her Indian counterparts and get this done.”
The Foreign Office has said it continues to raise concerns with the Indian authorities and that Cooper will do so again during her visit.
A Foreign Office spokesperson said: “We continue to raise concerns about Johal’s prolonged detention at every appropriate opportunity with the government of India, and the Foreign Secretary will do so again tomorrow.
“We have made clear that faster progress is needed to reach a resolution, including a full investigation into Johal’s allegations of torture.”
Cooper’s diplomatic trip to Asia has also included a visit to China, where she vowed to continue raising the case of imprisoned British citizen Jimmy Lai with the Chinese government.
The Foreign Secretary said a “really important” working relationship had been established between the UK and China, but she continues to face calls for a stronger stance on human rights and national security issues.
