The FCDO previously told the BBC it continued to raise the case of the Foremans directly with the Iranian authorities.
The UK government announced the temporary closure of its embassy in Tehran on Wednesday, saying it would now operate remotely.
“We have temporarily closed the British Embassy in Tehran, this will now operate remotely. Foreign Office travel advice has now been updated to reflect this consular change,” a government spokesperson said.
Britain’s ambassador and all consular staff were evacuated based on a security assessment and concerns for staff safety.
Bennett said if his parents were released, they had planned to go to the British embassy.
“The trouble is, their plan was to go to the embassy, was to try to get to the embassy because they feel that that’s safe ground and now… Where do they go? What do they do?” he said.
Bennett, who last spoke to his parents on Wednesday, said during the brief communication he’s been able to have, they’ve told him of the “unsafe” and “frightening” conditions of the prison.
“There are vermin in the kitchen and in beds. It is overcrowded, it’s even more overcrowding now that these protests have gone on in Tehran,” he said.
He added there were “fights that break out pretty much daily” which he could hear in the background during the phone calls with his mother.
Last year, Scottish National Party MP Brendan O’Hara told the BBC the couple were being used “bargaining chips” between Iran’s government and the West.