Sinn Féin and SDLP leaders have welcomed the initiative from civic unionism and others challenging what they said was a nationalist assumption that qualities such as rights, truth and equality were not inherent within unionism.

On Monday the group of 105 people mainly from different strands of unionism issued its response to two recent letters from “civic nationalism” groups in the North and South calling on the Government to protect the legal, human and language rights of Irish citizens in Northern Ireland.

The letter from political, academic, clergy, business, arts and sporting figures was described as “A positive challenge to Northern nationalists”. The signatories said they were motivated by a desire to “build a society for the betterment of everyone”.

They said they found it “frustrating and puzzling that civic unionism, pluralists and other forms of civic leadership have been rendered invisible in many debates focused on rights and responsibilities”.

The civic unionism initiative has prompted considerable discussion in Northern Ireland and a generally positive response from nationalism.

Sinn Féin’s Northern leader Michelle O’Neill said she welcomed this “initiative by those within civic unionism who insist that their views and voices are heard in the debate on the demand for rights and equality in northern society”.

“The campaign for rights and equality belongs to everyone. There is no such thing as nationalist equality or unionist equality. There is just equality for all,” she said.

Ms O’Neill added: “Last week our party chairperson, Declan Kearney, issued a call for civic society to create a common platform in defence of the Good Friday agreement which belongs to all the people of Ireland. I welcome this initiative from civic unionism as an important intervention into this debate.”

The SDLP leader Colum Eastwood in a welcoming letter to the civic unionism group said there was “no future if our political conversation continues to be locked in an arm-wrestle which no-one can win”.

“I hope that your letter is another important step in loosening that grip which has only resulted in a further polarisation of our society,” he said.

“I accept the constructive criticism that in too many cases uniformity has been painted upon unionism when the truth tells us that no such uniformity exists,” added Mr Eastwood.

“I know that the unionist peoples are much more diverse, open, creative and complex than the positions espoused by Arlene Foster. Be assured that the same diversity is true of Irish nationalism across this island,” he said.

Mr Eastwood added: “With all of the political volatility on these islands over recent years, the natural threads of communication between unionism and nationalism have suffered and have at times broken down. That breakdown is equally true of the broader relationship between the islands of Britain and Ireland.”