Church leaders have written to Britain's new Prime Minister Boris Johnson urging him to reconsider his "deal or no deal" approach to Brexit.

Mr Johnson has an uphill struggle ahead of him to negotiate a new Brexit deal - despite the EU already saying there are no concessions to be made - and promised in his victory speech on Tuesday to "get Brexit done" by the October 31 deadline.

"We are going to energise the country. We are going to get Brexit done on Oct. 31 and we are going to take advantage of all the opportunities it will bring in a new spirit of can do," he said, after securing the Tory leadership and 10 Downing Street in a ballot of party members. 

In an open letter to Johnson on Wednesday, Church leaders from several denominations said they felt "compelled" to challenge the very real possibility of Britain crashing out of the EU in a no-deal Brexit. 

The letter warns that failing to agree a Brexit deal with the EU will "hit those held back by poverty very hard indeed".

The Church leaders are asking the Government to publish evidence of the impact that a no-deal Brexit is likely to have on disadvantaged communities.

Specific concerns are raised in the letter around the cost and availability of medical supplies, food and energy. 

The Church leaders fear that the Government will be taking a "huge gamble" with the "basic needs of our poorest citizens and communities" if it simply assumes that EU member states will cooperate with the UK without any deal in place.

"At a time when increasing numbers of families have difficulties putting enough food on the table, we believe it is irresponsible to consider a course of action that is expected to make that situation worse," they write. 

"It is notable that assurances about our ability to cope with a no-deal Brexit, while frequent, are yet to be supported by substantial evidence."

The EU's chief Brexit negotiator said on Wednesday that a no-deal Brexit was not the EU's preference.

"We look forward to hearing what the new prime minister, Boris Johnson, wants, what are the choices of the UK," he said, according to the Guardian.

"Is it an orderly Brexit? ... Is it a no-deal Brexit? The no-deal Brexit will never be the choice of the EU, but we are prepared and for an orderly Brexit. We will work along the next few weeks or months with the new UK government in the best possible way, in the very constructive spirit to facilitate the ratification of the withdrawal agreement."

The full text of the Churches' open letter can be read here:

Dear Prime Minister

As Churches, we have a particular care and concern for the people in our society who are locked in poverty. Around the country, local churches are helping families to cope with the rising tide of poverty. Projects range from simple coffee mornings run by a few volunteers, to large projects such as foodbanks, homeless support, employment advice and debt counselling.

With this in mind, we are compelled to write expressing our urgent concern about your position that leaving the European Union without a deal is acceptable. Advice and data from multiple reputable sources, including the UK Government, indicate that failing to agree a deal will hit those held back by poverty very hard indeed.

The UK imports 10,000 shipping containers of food from the EU each day. These containers are part of long and complex integrated supply chains. Even minor disruptions to this chain have in the past rapidly had serious consequences. A no-deal Brexit will cause a huge and potentially crippling disruption. Government and many other reputable sources highlight the immediate risk of shortages and price rises. Over the longer term they point to the costs of new and less fluid supply chains increasing food bills for families.

Last year our partner, Trussell Trust, which represents around half of the UK's foodbanks, gave out a record-breaking 1.6 million 3-day supplies of food. At a time when increasing numbers of families have difficulties putting enough food on the table, we believe it is irresponsible to consider a course of action that is expected to make that situation worse.

It is also unclear how a wide range of other vital products and services will continue to be delivered in the event of a no-deal Brexit. Government, industry and charity sources indicate potential problems with both energy and medical supplies.

The UK Government's no-deal planning documents highlight that many of the difficulties caused by a no-deal Brexit can only be tackled in collaboration with the EU. The Cabinet Office states that for many issues we must seek accommodations with the EU which are "not within the UK's gift to unilaterally control or mitigate". In essence, the Government will be relying on the hope that our former EU partners are willing to cooperate even without an agreement – a huge gamble to take with the basic needs of our poorest citizens and communities.

The impacts of a no-deal Brexit are at best highly uncertain, and at worst deeply worrying. Our view that it would put at risk the welfare and safety of the poorest communities in the UK is formed on the basis of the best available evidence, including our presence in local communities in every part of the UK. It is notable that assurances about our ability to cope with a no-deal Brexit, while frequent, are yet to be supported by substantial evidence.

Evidence-free dismissals of well-founded concerns are at this stage both dangerous and inappropriate. Your Government's willingness to embrace a no-deal Brexit places upon it a responsibility to demonstrate that the most vulnerable in our communities, those locked in poverty, will not be harmed.

We ask that your Government urgently publishes its current evidence on the impact of a no-deal Brexit on disadvantaged communities. We would also be pleased to welcome you to one of our many projects to hear from those who a no-deal Brexit may most impact.

Rather than being absent from the debate, this evidence and these communities should be at the heart of our debates around Brexit.

We assure you of our prayers as you take up this challenging new role.

Yours sincerely

Revd Nigel Uden, Moderator of the General Assembly of the United Reformed Church

Mr Derek Estill, Moderator of the General Assembly of the United Reformed Church

Professor Clive Marsh, Vice-President of the Methodist Conference

Revd Dr Barbara Glasson, President of the Methodist Conference

Revd Dr Richard Frazer, Convenor of the Church and Society Council of the Church of Scotland

Revd Lynn Green, General Secretary, Baptist Union of Great Britain

Revd Alan Donaldson, General Director, Baptist Union of Scotland

Parchedig/Reverend Judith Morris, Ysgrifennydd Cyffredinol/General Secretary, Undeb Bedyddwyr Cymru/Baptist Union of Wales

Most Revd Mark Strange, Bishop of Moray, Ross and Caithness, Primus of the Scottish Episcopal Church

Commissioner Anthony Cotterill, Territorial Commander, The Salvation Army

Paul Parker, Recording Clerk for Quakers in Britain