An inquiry will be held into the government's handling of efforts to bring home Nazanin Zaghari-Ratcliffe, who was detained in Iran for six years.
The Foreign Affairs Committee (FAC) has announced an inquiry into "state-level hostage situations", which will take into account the detention of Nazanin and Anoosheh Ashoori.
Nazanin returned to the UK on March 17 after spending nearly six years imprisoned on charges of spying – something that was always denied.
Following their release, Hampstead and Kilburn MP Tulip Siddiq wrote to Tom Tugendhat MP, chair of the FAC, to ask for an inquiry.
She said Nazanin's husband, Richard Ratcliffe, agreed there was a need for a public inquiry to understand why the government failed to bring Nazanin home for so long and is still failing to secure the release of all British nationals held in Iran.
"I thank the FAC for agreeing to our call for an inquiry," she added.
She has asked the committee to consider why three Iranian officials who came to the UK in 2013 to negotiate repayment of a £400m debt were arrested when they arrived in the UK.
She also wants to know why the deal that the UK and Iran supposedly made in 2021 to resolve the debt and bring Nazanin home collapsed.
“I know that the Foreign Office cannot reasonably be held responsible for the arbitrary detention of its nationals abroad, but it also cannot escape scrutiny and challenge for its clear shortcomings in trying to secure their release – particularly from Iran," she said.
"Other countries including Australia, France, Germany, Canada and the US have had greater success in securing the fair treatment and release of prisoners held for leverage on false charges."
She spent months in isolation before being sentenced to five years at the notorious Evin Prison.
Ms Siddiq said she was grateful to the government for getting Nazanin home, but said: “Richard Ratcliffe and I have known since the start that Nazanin’s imprisonment was linked to the historic debt we owed to Iran, yet it was only after many years of pressure that this was finally resolved.
"While in Iran, Nazanin was blindfolded, handcuffed, interrogated and subjected to solitary confinement, sleep deprivation and torture.
"The government has serious questions to answer about why this was allowed to happen to an innocent British citizen, who was caught as a pawn in a political dispute between two countries."
The FAC said its inquiry will focus on the challenges that the Foreign, Commonwealth and Development Office (FCDO) faces when handling countries which use extra-judicial detention as a tool for diplomacy.
The high-profile releases of Nazanin and Anoosheh will be examined "as well as the precedent the FCDO’s response in these cases may set".
Processes and approaches taken by the government to try to secure the release of detainees will be looked at, as well as the likely impact the FCDO's approach could have on deterring other states from using the tactic.
It will also "consider options for multilateral action to further deter such behaviour".
Mr Tugendhat said: “Nazanin and Anoosheh’s homecoming is wonderful news, but long overdue. After years of imprisonment, in extremely difficult circumstances, Nazanin and Anoosheh are right to ask for answers.
“Iran is not the only country engaging in state hostage taking. The tactic is fast becoming a tool of choice for authoritarian states and recent high profile cases have highlighted the challenges governments face when securing the release of hostages held captive by states.
“This inquiry will examine the support provided by the FCDO to hostages in recent cases, as well as take a look at the broader picture and ask how the Government can clamp down on the practice internationally.”
Written submissions are being accepted by the inquiry until May 13.
The Foreign Office has been contacted.
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