An outspoken Catholic nun living in Syria has denied suggestions that she believes the toppling of President Bashar al-Assad would bring an end to Christianity in Syria.

Instead, Mother Agnes-Mariam says that could be the consequence if religious extremists were to seize on a power vacuum left by his deposition.

The Lebanese-born nun, who is Mother Superior of the monastery of St. James the Mutilated – the oldest monastery in the Qalamoun area of Syria – is part of the Syria Solidarity Movement and has recently finished a speaking tour in the US.

Now in the UK, Mother Agnes-Mariam told the BBC yesterday that supporting Assad is not her goal; rather, she said, it is to bring peace to Syria and to find a viable alternative to the current government before any attempts are made to overthrow the beleaguered dictator.

"It's not about Assad; it's about the Syrian population and the fate of a whole country," she said. "If you have a tumour, you do not kill the patient; you have to bypass the problem to be able to give the good answer, and now the good answer is a peaceful process.

"It will be the end of the civilised world today in Syria, where the alternative is the fundamentalist and extremist jihadists that are throwing violence and terror everywhere."

Mother Agnes-Mariam denied that she was working for President Assad, saying suggestions that she was were "deprived of any root in reality" and only seeking to undermine and discredit an "honest and fair work" to help Syrians.

She also thanked the British government and people for voting against military intervention in Syria, saying that this had "opened widely a door for peace".

However, Mother Agnes-Mariam acknowledged that the greatest challenge facing Syria was the lack of a credible opposition.

"The big problem is that we are talking about toppling a government while we don't have an alternative," she said. "It's good to look at the Syrian population and to look who is representing effectively on the ground the Syrian population."

Mother Agnes-Mariam also reinforced her controversial belief that videos purportedly showing chemical weapons attacks in Damascus on August 21 were fabricated.

"I am sure 100 per cent," she said. "I have new evidences through observation and metadata."

Mother Agnes-Mariam denied accusations that in order to orchestrate the evacuation of several thousand families from Damascus, she had agreed to hand over 600 people to government forces.

"[The accusation] is false, it's false," she said. "We have been working with the families, they asked us for evacuation. I entered on danger of my life to talk with the military council; there was a battle inside, we were going to be killed and then to be abducted. Finally a rebel leader protected us because he wanted his family to go out and that's how we could evacuate 7,000 families. Nobody was imprisoned; on the contrary they were treated with the best standards."