Members say proposals could create a climate of fear and distrust.
A coalition of voluntary organisations, ethnic community groups and MPs is to hold a major rally in October to oppose the Prime Minister's new proposals on terror law.
The organisations, which include human rights organisation Liberty, the Muslim Association of Britain and the Refugee Council, issued a joint statement shortly after Tony Blair announced a series of anti-terror measures on 5 August.
They described the Prime Minister's move as "against the post-7 July consensus" and argued that it would criminalise the majority of those in the Muslim community who want to help tackle terrorism.
The Refugee Council said the plans, which include the use of sanctions against those accused of terrorism anywhere in the world, not just in the UK, would create a climate of fear and distrust towards the authorities among the refugee community. It argued that asylum seekers marked as terrorists for dissent towards their own governments could face sanctions from UK authorities. "It would frighten refugees and asylum seekers, and make them reluctant to co-operate with the authorities," said a spokeswoman.
Ihtisham Hibatullah, a spokesman for the Muslim Association of Britain, said the statement was an immediate reaction and just the first step in a campaign that aims to show how British ethnic minority communities reject the proposals. He said the next step would be a major rally near Parliament to lobby ministers and MPs, but the timing would depend on when Parliament returned.
Doug Jewell, a spokesman for Liberty, said: "These events usually gather a couple of hundred people, but given the number of agencies involved we are expecting more than a thousand for this one."
Jewell expects a number of contentious Bills to be introduced in October.
"The PM's proposals include the closure of places of worship, which would require new legislation," he said. "This would be counter-productive because both the police and the Government need to work with communities to fight terrorism, not criminalise them."
Number 10 also wants to delay refugees' rights to appeal their deportations until after they have been sent back to their countries of origin. Jewell believes this could be included either in a new Bill or in the Immigration, Asylum and Nationality Bill, which is currently going through Parliament.
"The forthcoming measures are a mixture of new guidelines, new legislation and amendments to existing laws," said Jewell. "It is all very shambolic. There is no other word."
He added that the Government should focus on strengthening current law.
"There may be gaps that have yet to be identified, but there is more than enough legislation," he said.
The Liberty-led coalition also includes MPs Tony Lloyd and Sadiq Khan, Lord Bhatia, Baroness Ludford and the Mayor of London.