The home secretary has been urged not to “play into the hands of those seeking to build division” by more than 200 community groups across the UK who have described Shabana Mahmood’s plans to overhaul the asylum system as “cruel” and “ruthless”.

Last month Mahmood unveiled policies that she hopes will tackle bogus asylum claims and reduce the numbers of people trying to cross the Channel in small boats, including the end of permanent protection for refugees, the escalated removal of families with children whose claims have been refused, and scrapping the legal requirement to support destitute asylum seekers.

The changes would also formally end the automatic right to family reunion for refugees before it was suspended in September.

In an open letter seen by the Guardian, 225 organisations, including charities, businesses, sports, faith and arts groups have told Mahmood they “reject” the plans.

They said: “In communities up and down the country, we are proud to show warmth and kindness to refugees … We know that your cruel new plans do not represent us, our communities or who we are as a country.

“You said it was a moral mission to resolve division. We agree. The responsibility to end the divisive politics, racist rhetoric and demonising language of the past lies with all political leaders. Your ruthless new plans to erode refugee rights and the harmful language used by politicians in recent weeks will only feed the hostility in our communities. We know, given the chance, refugees do so much to enrich our communities.

“People who have fled the horror of war and persecution, suffering terrible trauma, need support to heal and rebuild their lives. Instead, this government is choosing cruelty over compassion. We – communities across the UK – are standing together to reject your plans. Now is not the time to play into the hands of those seeking to build division between local communities and refugees.”

The signatories include African and Caribbean Support Organisation Northern Ireland, nationwide branches of the charity Care4Calais, Fairtrade Greater Manchester, Govan Community Project, Toxteth Women’s Centre, West Cornwall Against Racism and City and Town of Sanctuary groups from places including Abergavenny, Barnsley, Birmingham, Calderdale, Hastings and Norwich.

Campaigners from some signatories were expected to attend a Home Office demonstration on Friday before a week of Communities Together for Refugees solidarity events around the UK, including Christmas markets, craft sessions, food and performances, organised in collaboration with the Together With Refugees coalition. The public has been invited to print out their own posters in support.

Minda Burgos-Lukes, of Together With Refugees community organising network, said: “Through our work and personal experiences, we see every day the courage of people forced to flee their homes and the compassion they are met with in our communities.

“The far right marches and attempts to spread fear do not reflect what we witness on the ground.”

In the foreword to the policy paper outlining the plans, Keir Starmer said: “There is nothing compassionate about allowing the vile trade in people smuggling that perpetuates illegal migration … the UK’s current asylum regime is a significant pull factor to that trade.”

In the same paper, Mahmood said: “This country’s asylum system was designed for an earlier and simpler era and has not been updated to reflect our changing times.”