The detention of an Iranian delegation at Heathrow Airport almost a decade ago may have been behind the arrest of Nazanin Zaghari-Ratcliffe, former foreign secretary Jack Straw has claimed.

Mr Straw said the Iranian team arrived in the UK in 2013 to discuss the repayment of a historical £400 million pound debt Britain owed for a consignment of tanks that was never delivered.

Although they had been properly issued with visas, the negotiators were held by border officials and sent back to Iran a few days later, Mr Straw said.

He believes the subsequent detention of Mrs Zaghari-Ratcliffe may have been Iran’s way of retaliating.

Britain’s agreement to settle the debt – relating to the cancellation of an order for 1,500 Chieftain tanks after the overthrowing of the Shah of Iran in 1979 – was key to securing the release of Mrs Zaghari-Ratcliffe and her fellow detainee Anoosheh Ashoori.

Mr Straw, who was Labour’s foreign secretary from 2001 to 2006 and has written a book about UK-Iran relations, said the whole affair may have arisen because of the way Britain antagonised Tehran.

“There was full disclosure about why they needed visas and they were given those visas. They got on the aeroplane, they arrived at Heathrow,” he told BBC Radio 4’s The World at One.

“There was no welcoming party. Instead, border officials detained them, locked them in an immigration centre for two or three days and then deported them.

“The Iranians subsequently claimed they were ill-treated. I have no idea whether that was the case, but it was certainly not what they were expecting nor what we should have done.”

No member of the Iranian government was permitted to come to the UK following the sacking of the British embassy in Tehran by protesters in 2011, which Mr Straw said possibly explains the delegation’s treatment.

“What I surmise, and it is only surmise, is that at this stage the more hardline elements in the regime decided they were going to take some kind of direct action,” he said.

“They decided that if somebody suitable presented themselves, which I am afraid Nazanin did when she arrived there in 2016, they would arrest her and charge her with spurious spying charges.”

During his time at the Foreign Office, the tank debt had not been raised as an issue that needed resolving, Mr Straw said.

“I dearly wish that it had come up. I am pretty certain that if it had been flagged to me properly I would have said, ‘Hang on a second, we just need to pay this money,'” he said.

Mrs Zaghari-Ratcliffe’s local MP Tulip Siddiq said she will be asking the Commons Foreign Affairs Committee to investigate Mr Straw’s claims.

“I owe it to Nazanin to ask questions as to why it took so long to bring Nazanin back and why the debt wasn’t paid for so long, which we know was key,” she said.