Charities are "not ready for a no-deal Brexit" and leaving the European Union without a deal would be detrimental to civil society, more than 85 organisations have warned the Prime Minister.
In a letter coordinated by the Brexit Civil Society Alliance and signed by organisations including Acevo, Friends of the Earth, the Northern Ireland Council for Voluntary Action and the National Union of Students, Boris Johnson is warned of the ramifications for charities and the communities they serve of pursuing a no-deal Brexit.
Johnson is also urged to engage with the sector on Brexit and provide support to charities affected by it.
"Civil society faces the same Brexit-related impacts and uncertainties as business, and yet we have not had adequate support, resources and engagement from the government," the letter says.
"We urge you to better engage with civil society, including across the devolved nations, throughout the next stages of the Brexit process.
"Leaving the EU without an agreement will have drastic and wide-ranging implications for citizens and communities, who deserve to be heard."
The letter comes the day after the government formally requested the prorogation of parliament for four weeks from mid-September to mid-October, before the UK’s expected departure date from the EU on 31 October.
Johnson has repeatedly said he would be prepared to leave the EU without a deal if there were not changes to the previously agreed deal.
But the letter says that no deal could have profound implications for the Good Friday Agreement and the peace process in Northern Ireland, a substantial impact on the economy and trade and the overnight loss of EU agencies that monitor and ensure compliance with the law.
These EU agencies oversee areas such as food standards, animal welfare and the environment.
The letter says: "A growing body of evidence shows that a no-deal Brexit would be detrimental to civil society and the communities that we work with.
"The uncertainty, the predicted economic shock, the prospect of legal uncertainty as well as the regression in rights and standards present a profound risk to the values civil society stands for."
The move comes in the wake of a recent letter from Anne Fowlie, chief executive of the Scottish Council for Voluntary Organisations, that also warned a no-deal Brexit would cause charities to collapse and leave a "vacuum of support" in local communities.