David Cameron has urged the Sudanese government to lift the "barbaric" death sentence handed to a woman for marrying a Christian.
The Prime Minister joined Ed Miliband, Nick Clegg and Tony Blair in condemning the treatment of Meriam Ibrahim - who gave birth to a baby daughter this week while shackled in her cell.
Meriam Yehya Ibrahim (pictured here with husband Daniel Wani) has given birth to a baby girl in a Sudanese prison
Cameron said he was "absolutely appalled" when he heard about the plight of the 27-year-old.
"The way she is being treated is barbaric and has no place in today's world," he told The Times.
"Religious freedom is an absolute, fundamental human right.
"I urge the government of Sudan to overturn the sentence and immediately provide appropriate support and medical care for her and her children.
"The UK will continue to press the government of Sudan to act."
Meriam Yehya Ibrahim gave birth to a baby girl - whilst in shackles - her husband claims
Daniel Wani meets his daughter for the first time
Ibrahim was raised a Christian by her mother and has refused to renounce the faith.
However, a court ruled earlier this month that she is Muslim because that was her father's faith.
Her Christian marriage was annulled and she was sentenced to 100 lashes for adultery and death by hanging for renouncing Islam. Sex outside a "lawful relationship" is regarded as adultery under Sudanese law.
She is being held along with the 20-month-old son she also has with husband Daniel Wani.
Wani is appealing his wife's execution, which officials said won't be held until after Ibrahim gives birth and nurses her infant.
The father is not even allowed to care for Martin because he is a Christian and his son is considered a Muslim.
Former PM Mr Blair described the case as a "brutal and sickening distortion of faith".
Human rights organisation Amnesty International UK told the Huffington Post UK that Ibrahim it would continue to appeal for her immediate release.
Kathy Voss, Amnesty UK’s Individuals at Risk Campaigner, said: “There are now three innocent people in that cell.
“The way Meriam has been treated is sickening, and it has appalled the world. This really is the stuff of nightmares."
The case has prompted questions over whether the UK should continue giving aid to countries which do not respect human rights.
Conservative North Somerset MP Liam Fox, the former defence secretary and shadow foreign secretary, said the Government needed to think again about aid.
"Religious tolerance is something that the UK should be promoting at every opportunity," he said.
"We need to ask ourselves whether it is acceptable too be giving taxpayers' money in aid to states which allow treatment such as that handed out to Meriam Ibrahim."
Mrs Ibrahim's husband said his son has become sullen and withdrawn since being incarcerated with his mother.
He added that his wife was under pressure to convert her religion so she can leave prison but said she was "committed" to her right to religious freedom.
Gabriel Wani said: "I’m just praying for God. He can do a miracle. Everyone is depressed. You don’t believe it. It’s shock."