The Equality and Human Rights Commission wants the plans dropped and has warned there is a high risk that British and European laws will be broken, in a letter seen by the Guardian.
Serving officers represented by the Black Police Association have also damned the plans as a "concession to racism" as opposition to the measures intensifies.
The issue threatens to test the credibility of Conservative claims to be an inclusive party and drag the government into a dispute over race.
The Home Office says it intends to press ahead and introduce the guidance allowing race to be taken into account when a police officer stops someone if it is judged to be relevant. It says race cannot be the sole reason for deciding to conduct a search, and the government insists the new measures will "protect civil liberties".
The issue of the police stop-and-search powers is particularly controversial because officers are more likely to target a minority ethnic person than someone who is white. African-Caribbean people are already at least six times more likely to be stopped than white people under powers where an officer has reasonable suspicion to carry out a search.
The Home Office proposals cover stops where officers do not require reasonable suspicion, a power they have under section 60 of the Public Order Act, meaning police have maximum discretion. For these stops black people are 26 times more likely than white people to be targeted. Critics say this is blatant discrimination.
A Home Office spokesperson said: "The proposed new guidelines make clear that ethnicity may not be used as the sole basis for stopping and searching anyone under section 60." But in its letter to the government, the commission said: "We consider there is a significant risk that this provision will result in race discrimination."
It adds there is a "high risk" it may lead to "a degree of racial profiling".
The commission says provisions on freedom from state intrusion and discrimination are likely to be broken unless the government backs down: "There is a high risk these powers would breach article 8, and or 14 of the European convention on human rights, and section 29 of the Equality Act 2010."
The Home Office plans to allow police to search people where there is no eyewitness description are also causing alarm. The measure will allow descriptions taken from CCTV images to be used, which is uncontroversial. But the commission and some police officers say the Home Office proposal is too widely drawn and may allow stops on the basis of "outright racial prejudice or hatred".
Opposition also comes in a letter from the Black Police Association, and signed by Doreen Lawrence, whose son Stephen was killed by racists. The case of Stephen Lawrence led to measures aimed to tackle alleged police discrimination, some of which the government will abolish.
This includes the recording of stops and searches by officers, which allows for the gathering of data on the over-targeting of minority ethnic people by police.
In the letter, the black police officers, Lawrence and a coalition of minority ethnic groups say: "The new proposal to widen to widen this area opens the door to racial targeting that could be based on gossip, malice and outright racial prejudice.
"This particular change along with the abolishment of stop and account could vastly increase the stopping of young black men which is already wholly disproportionate, and would worsen police and community relations. By changing the guidance to allow a citizen's ethnicity to provide reasonable cause for the use of this intrusive power will result in the large-scale legitimisation of racism in policing.
"We believe that such a move will be seen as deeply provocative and a dangerous concession to racism."
The Home Office guidance reads: "There may be circumstances, however, where it is appropriate for officers to take account of an individual's ethnic origin in selecting persons and vehicles to be stopped in response to a specific threat or incident, but this must not be the sole reason for the stop. For example, when the authorising officer reasonably believes those likely to be responsible are associated with particular ethnic identities and passes that information on to the officers exercising the powers."
The Guardian has also learned that a national community panel set up to reduce the over-targeting of minority ethnic people was abolished in summer. It had been under the wing of the home office, but the last government transferred it to the National Policing Improvement Agency. Local panels were intended to replace it but they are not yet functioning.
Stops carried out under section 44 of the Terrorism Act 2000 have already been dropped after the European court of human rights struck them down. Last year over 100,000 stops were carried out under section 44, without police making a single arrest for terrorism.
The American civil rights leader Rev Jesse Jackson has said Britain's moral authority is being damaged by the government's failure to stop the police discriminating against ethnic minorities
Isabella Sankey, policy director for Liberty, said: "It makes no sense to tighten up section 44 stop and search while making section 60 more discriminatory. A young, black man is already 26 times more likely to be stopped and searched under section 60 than his white counterparts – we urge ministers to think again."
The Guardian
