Christian Climate Action (CCA) is inviting people to take part in 40 days of action over Lent.
The campaign gets underway on Ash Wednesday on 26 February with a vigil outside Westminster Cathedral at midday that will then process to Westminster Abbey and Parliament Square.
Members of CCA are looking to the Catholic Church to follow the lead of the Church of England, which last week committed to net zero emissions by 2030.
In a symbolic act, priests will mark a cross on the foreheads of worshippers using fake crude oil instead of the traditional ash.
The CCA said that the use of oil was to symbolise human mortality but also "human frailty as we are currently losing the fight against the over consumption of fossil fuels".
The 40 days of action will continue through Lent with a focus on "lament for the climate change and ecological crisis", and prayers for leaders to take urgent action.
The CCA said that some of its members may engage in civil disobedience to pressure government to commit to net zero carbon emissions by 2025.
Nick Cooper, Christian Climate Action member, said: "This is about system change triggered by personal growth. We invite everyone to journey with us into the wilderness of Lent and encounter the 'quiet voice' so often hidden from us in daily life.
"We need desperately to hear that sacred voice calling us together as a global community, to share what we have left, learning to live simpler more connected lives, and find the courage to take up civil disobedience in the face of an ever more desperate climate and ecological crisis.
"We need to take courage and stop denying the power that we hold as one sacred and interconnected body."
The 40 days of action have the support of Christian environmental group Operation Noah and Dr Ruth Valerio, global advocacy and influencing director of Tearfund, who is also the author of Saying Yes to Life, the companion book for the Church of England's first ever green Lent campaign.
Dr Valerio said: "The window to address climate breakdown is closing rapidly and the UK government needs to act by getting our finances out of fossil fuels overseas, increasing investment in renewable energy and getting on track to achieve our own net zero commitment.
"Lent, which is a time of reflection and commitment, is an important time to pray for our politicians to have the courage to take action. The physical presence of this vigil is a reminder of this."
Nicky Bull, Chair of Operation Noah said: "At Operation Noah we are supportive of Christian Climate Action's plans for a round-the-clock vigil in Parliament Square during Lent 2020.
"In this important year for action on the climate crisis, we endorse the principles and values of Christian Climate Action and wholeheartedly support a call for more widespread divestment from fossil fuels and reinvestment in alternative sustainable energy."
Rev Daniel Woodhouse, a Brighton-based Methodist minister, said that the CCA campaign was a great way of bringing the whole church together to explore what faithfulness looks like within the context of caring for the environment.
"'The climate crisis is the defining issue of our generation, which is already having devastating affects around the world," he said.
Sr Katrina Alton, a Sister of St Joseph of Peace who lives in Nottingham Diocese, will be one of the many campaigners joining the vigil on Ash Wednesday.
She said that the Government needed to take action "now" on climate change.
"In his most recent apostolic exhortation, 'Querida Amazonia', Pope Francis has defined 'ecological sin' not only as 'actions', but also 'inaction', that crucify the poorest and the environment," she said.
"The Pope goes a step further and says, 'It is a sin against future generations'.
"Our presence here in Parliament Square for these 40 days of Lent is a sign of our personal and collective commitment to make the sacrifices required to put pressure on our government to tell the truth and act now."