In this file photo dated Monday, Jan. 16, 2017, Richard Ratcliffe, husband of imprisoned charity worker Nazanin Zaghari-Ratcliffe, poses for photo outside the Iranian Embassy in London.
Richard Ratcliffe started his fast on Sunday outside the British government's Foreign Office in central London.
He plans to maintain a ``constant vigil'' by sleeping in a tent outside the building's main entrance in an effort to pressure Prime Minister Boris Johnson to secure the release of his wife and other detained dual British-Iranian nationals, Amnesty International said.
Zaghari-Ratcliffe served five years in prison after being taken into custody at Tehran's airport in April 2016 and convicted of plotting the overthrow of Iran's government, a charge that she, her supporters and rights groups deny.
In May, she was sentenced to an additional year in prison on charges of spreading ``propaganda against the system'' for having participated in a protest outside the Iranian Embassy in London in 2009 _ a decision upheld this month by an appeals court. The verdict includes a one-year travel ban, meaning she wouldn't be able to leave Iran until 2023.
Ratcliffe went on a 15-day hunger strike two years ago outside the Iranian Embassy, a move he credits with getting their 7-year-old daughter Gabriella released.
``We are now giving the U.K. government the same treatment. In truth, I never expected to have to do a hunger strike twice. It is not a normal act,'' Ratcliffe said on his change.org petition.
He said Iran remains the ``primary abuser'' in Nazanin's case, but the ``U.K. is also letting us down.``
``It is increasingly clear that Nazanin's case could have been solved many months ago - but for other diplomatic agendas. The PM needs to take responsibility for that.''
Zaghari-Ratcliffe was employed by the Thomson Reuters Foundation, the charitable arm of the news agency, and was arrested as she was returning home to Britain after visiting family. Rights groups accuse Iran of holding dual-nationals as bargaining chips for money or influence in negotiations with the West, something Tehran denies.
Iran doesn't recognize dual nationalities, so detainees like Zaghari-Ratcliffe can't receive consular assistance.