Around 12 people reaffirmed their baptismal vows in London's Trafalgar Square on Tuesday as part of the Extinction Rebellion.
Their heads were doused with water from a paddling pool and marked with the sign of the cross.
The ceremony was performed by Rev Jon Swales, Mission Priest at the Church of England's Lighthouse Church in Leeds.
He said: "Before we reaffirm our baptism we are going to be signed with a cross. That symbol that was there to say 'that's how rebels die', but instead it becomes the focus of our hope."
One of those reaffirming their vows was Holly-Anna Petersen, 31, a member of Christian Climate Action.
She said: "I wanted to be baptised here because this is the outworking of my faith. Being here, making a stand for God's creation, is part of my worship.
"Jesus was the ultimate rebel, whose bravery in speaking out against injustice led not only to his arrest but his death.
"Being here on the streets, sharing community and standing up to oppressive powers, feels very much like the early church."
Christians have been taking part in the Extinction Rebellion all week calling on the Government to do more to address climate change.
They have turned Lambeth Bridge into a 'Faith Bridge' with baptisms, a daily Eucharist and foot washing.
Christians, including clergy, have been arrested by the police for taking part in the protests. Among them was Rev Helen Burnett, vicar St Peter & St Paul's Chaldon.
Before her arrest she said: "We are standing here today to span the gap between the truth we know about the climate emergency and the action that our government must take to avert the 6th mass extinction.
"We will do that by standing together as people of all faiths and none holding our love for the earth in our courageous hearts, singing our songs, praying our prayers and dancing our way towards change."