"I feel disgusted and betrayed".
Billy Irving said he could "never forgive" officials who he claimed did not do enough to help him. Mr Irving, the first of the so-called Chennai Six to arrive back in the United Kingdom, landed at Glasgow Airport on Wednesday.
The group, known as the Chennai Six, were convicted of carrying unlicensed firearms and ammunition in October 2013 and jailed along with 29 other men.
The 37-year-old is former corporal with the Parachute Regiment who served in Afghanistan and Iraq.
The former soldier was among five other Britons held in India on weapons charges related to an anti-piracy mission.
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After years of campaigning, the men won an appeal against their convictions last month and were given permission to leave India, flying back to the United Kingdom earlier this week.
His fiancee, Yvonne MacHugh, led a high profile campaign to have Mr Irving and his former colleagues released from the "hell hole" prison.
She accused current incumbent Boris Johnson of "hypocrisy" for saying the FCO had worked on the case "unstintingly".
"I will never forgive the FCO", she added. They complicated situations and moved goalposts.
Ms MacHugh said the prisoners would have been released two years ago if the FCO had done their jobs properly.
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During his four years in prison, Irving - from Paisley, Renfrewshire - contracted dysentery and lost 19kg (three stones). He missed the birth of son William, who until now had only met his father three times in jail.
Mr Irving said: "To finally smell fresh air and feel cold, wet rain on my face is the most fantastic feeling in the world".
In response, the FCO said that since the men's arrest in October 2013, the case has been raised more than 50 times at ministerial level and nine times with the Indian prime minister.
A spokeswoman for the Foreign and Commonwealth Office said it had worked "tirelessly behind the scenes" to reunite the men with their families.
"This included lobbying on their behalf, visiting them in prison, updating their families, and maintaining close with their legal team".
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