British-Iranian charity worker Nazanin Zaghari-Ratcliffe, held in Tehran for six years, has called for all "unjustly detained" prisoners in the country to be freed.

Speaking publicly for the first time since her release, Zaghari-Ratcliffe thanked those involved in the campaign to secure her exit from Iran but told reporters at the House of Commons that she was disappointed it took five different UK foreign ministers to convince Tehran to let her go. 

"What happened now should have happened six years ago," she said.

Zaghari-Ratcliffe, a dual citizen, was arrested by revolutionary guards at Tehran airport in 2016, while trying to return to Britain with her then 22-month-old daughter Gabriella after visiting her parents.

She was later convicted by an Iranian court of plotting to overthrow the clerical establishment. Her family and the foundation denied the charge.

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She went on to thank her "amazing wonderful husband" Richard Ratcliffe for his intensive campaigning to bring his wife home, but disagreed with him for thanking current Foreign Secretary Liz Truss for the government's efforts.

Joined by her husband and the family's local MP Tulip Siddiq for the news conference in Westminster, she said her return had been "emotionally tough" after missing six years of her daughter's upbringing. Their seven-year-old Gabriella was in the front row. 

"Coming back to a daughter who is nearly eight – I left her when she was not even two – there is a whole lot to catch up," said Zaghari-Ratcliffe.

Speaking about her experience in Iran, she said: "There is no other way around it. It will be with me. It's never going to leave you alone. But I think at the moment I would rather just focus on the moments of coming back."

Her husband also spoke, saying the ordeal had been "a long struggle" but he was "immensely pleased and proud of my wife. Proud to have her home. Proud that we get to be a normal family again." 

Zaghari-Ratcliffe is one of several prisoners to be exchanged between Tehran and the West following months of talks on reviving a 2015 nuclear deal with Iran. 

The decision to release her alongside UK dual national Anoosheh Ashoori also came after Britain finally repaid a historic debt of 400 million pounds ($520m) to Tehran.

Iran's clerical rulers said Britain owed Iran the money that Iran's former monarch, the Shah, paid up front for 1,750 Chieftain tanks and other vehicles, almost none of which were delivered after the Islamic Revolution of 1979 toppled the U.S.-backed leader.