Nineteen church leaders have written to Prime Minister Boris Johnson calling on him to set ambitious goals for cutting emissions.
They want him to pledge to cut UK emissions by at least 75 per cent, from 1990 levels, by 2030 when he submits the country's first climate plan under the Paris Agreement.
The Paris Agreement commits countries to keeping temperature rises "well below" 2C above pre-industrial levels, and pursuing efforts to limit them to 1.5C, which is seen as the threshold beyond which the worst impacts of climate change will be felt.
Because of Brexit, the UK has to submit its own national climate plan to the UN climate body, the UNFCCC.
The letter to the Prime Minister was signed by the Church of England's lead bishop for the environment, Rt Rev Nicholas Holtam, the Bishop of Salisbury, as well the Archbishop of Wales, and leaders from the Church of Scotland, the Baptist Union, Methodist Church, United Reformed Church and Quakers among others.
They write: "In 2021, the UK has the chance to be a true global leader. 2021 is a critical year to tackle the climate crisis and the UK is uniquely placed to lead the world in ambitious action as the President of the COP26 UN climate talks.
"Christian Aid, their supporting churches across the UK, and their local partners around the world expect your Government to tackle climate change in a way that is fair and just for the world's poorest people. That's why today we, as representatives of those churches, are writing to you in support of the petition being submitted to you by Christian Aid, signed by over 57,000 of their supporters, calling for action."
They call on the Government to commit to cutting emissions solely through domestic action and based on the scientific evidence provided by the Committee on Climate Change.
The proposal is more ambitious than what the Government currently has planned.
The Committee on Climate Change has recommended the UK should commit to cutting emissions by at least 68 per cent on 1990 levels by 2030, under its Paris plans.
The committee said the 68 per cent cut would be a "clear progression" from existing commitments under domestic law, which require a 61 per cent reduction by 2030.
In a letter to Business Secretary Alok Sharma, the advisory committee said cuts of that level would be in line with the UK's international commitments and would place the UK "among the leading countries in climate ambition".
The church leaders also want the prime minister to pledge financial support for climate-vulnerable countries, assistance for communities needing to adapt to the impacts of climate change, and help to get renewable energy technology.
They conclude: "As we look with hope to the securing of a critical deal in Glasgow next year, churches across the UK are committed - together with Christian Aid and its supporters - to working with you and your Government to help deliver a national climate plan that ensures climate justice for the world's poorest people."
The letter is accompanied by a petition, signed by 57,000 people, demanding a New Deal for Climate Justice, which "puts the world's poorest and most vulnerable communities at the heart of global climate policy, stops the expansion of fossil fuel projects and invests in rapidly decarbonising the UK economy."
Pete Moorey, Christian Aid's head of campaigns and UK advocacy said: "The climate emergency is the great moral issue of our time. The people suffering the most are those that have done the least to cause it. That's why church leaders from across Britain have stood together to call on Boris Johnson to set a bold commitment for other countries to follow.
"As president of the UN climate summit next year, the UK will be encouraging other nations to come forward with ambitious plans. The UK's own climate pledge must set a high bar for action, anything else would be a failure of leadership.
"After the recent decision to cut UK overseas aid, the UK has a moral duty to make inequality and injustice in the world's poorest countries central to next year's summit. People around the world facing the reality of climate change right now are counting on it to be a success."