Labour is piling pressure on the government on Sunday, with Labour's top two politicians calling for Boris Johnson to resign.
Johnson is under pressure over comments he made about Nazanin Zaghari-Ratcliffe, a British Iranian woman being detained in an Iranian prison. He suggested that she was teaching journalism, something that is illegal in the country and risks doubling her existing five-year sentence.
"This is the latest in a long list of gaffes made by our foreign secretary," said Khan.
"I think he's got to go. He's our foreign secretary, whose job is diplomacy and representing the best interests of our country and if Theresa May was a strong Prime Minister she'd have sacked him a long time ago," he added, speaking on the BBC's Andrew Marr Show on Sunday.
Corbyn told the Observer late on Saturday night: “We’ve put up with Johnson embarrassing and undermining our country with his incompetence and colonial throwback views and putting our citizens at risk for long enough. It’s time for him to go.”
Meanwhile, environment secretary Michael Gove said he did not know why Zaghari-Ratcliffe was being held. Her employer, the Thomson Reuters Foundation, and family say she was detained in 2016 after taking her daughter on holiday to visit family.
When this was put to Gove, also appearing on the Andrew Marr Show, he said: "In that case I take exactly her husband's assurance in that regard. Her husband said she was there on holiday, and her husband is the person who should know."
Zaghari-Ratcliffe's husband Richard is due to speak with Johnson today.