A petition urging the release of father-of-two Jim Fitton, 66, has received more than 97,000 signatures in the three days since it was launched.
His daughter Leila and her husband Sam Tasker, from Bath, in Somerset, have said the sentencing this month is expected to coincide with a long-planned celebration of their wedding.
“There is never a good time for something like this to happen but we are one week away from what should be the happiest day of our lives, and the culmination of more than two years of planning, and it’s been turned into an absolute living nightmare," they said.
“We have accepted the fact that, without timely intervention from the FCDO (Foreign, Commonwealth and Development Office), Jim will be unable to attend this ceremony too.”
Mr Fitton has been detained in Iraq for five weeks after being accused of attempting to smuggle historic artefacts out of the country.
His family said Mr Fitton collected stones and shards of broken pottery as souvenirs while visiting a site in Eridu, in the country’s south-east, as part of an organised geology and archaeology tour.
But they added the items were judged to be artefacts under Iraqi law and the charge levelled at Mr Fitton states “whoever exported or intended to export, deliberately, an antiquity, from Iraq, shall be punishable with execution”.
His case in connection with the March incident is expected to go for sentencing in the week beginning May 8.
Mr Fitton’s family described the response to the petition as “unbelievable”, They added in a statement: “Jim really appreciates the support from old colleagues, good friends, kindred spirits, and complete strangers who have not allowed this to go unnoticed.
“We will continue to fight while we continue to have you at our backs.”
Mr Fitton worked as a geologist for oil and gas companies during his career and lives in his adopted home of Malaysia with his wife, Sarijah.
Wera Hobhouse, Liberal Democrat MP for Bath, has raised his case with ministers in the House of Commons.
The family said their lawyer has drafted a proposal under Iraqi law to have the case closed before trial, but they need the Foreign Office to “put their weight behind the plan and endorse it” so they can secure a high-level meeting with judicial officials in the country.
The proposal cites the “clear lack of criminality, that Jim is a victim of poor guidance and circumstance, and also cites the huge investment that the UK has made in the Iraqi governmental and judicial framework through FCDO funding in the past few years”.
The family statement, via an update on the petition website, also explained: “Leila has not seen Jim for more than two years due to Covid travel restrictions.
“We held a small Covid wedding ceremony in Bath in August of last year for close friends and our British family members, mostly on my side.
“We have, since then, been planning a larger celebration in Malaysia with all of Leila’s extended family.
“This is scheduled on May 8. Obviously there is never a good time for something like this to happen, but we are one week away from what should be the happiest day of our lives, and the culmination of more than two years of planning, and it’s been turned into an absolute living nightmare.”
“It’s impossible to imagine what Jim and his family are going through, especially as Sam and Leila are planning their wedding," said Ms Hobhouse.
“We are pressing the Foreign Office to intervene, but sadly they are continuing to refuse. I cannot understand why the Foreign Office is not intervening when Jim’s life lies in the balance.
“The Foreign Office must do everything in their power to bring Jim back home to his family.”
The Foreign Office has said it is providing consular support and is in contact with the local authorities.
“We understand the urgency of the case, and have already raised our concerns with the Iraqi authorities regarding the possible imposition of the death penalty in Mr Fitton’s case and the UK’s opposition to the death penalty in all circumstances as a matter of principle,” said Foreign Office minister, Amanda Milling, in a letter to Ms Hobhouse last week.