Stop and search powers should be scrapped entirely after 40 years of alienation, a campaigner has claimed, despite moves by the Home Secretary and police forces to increase transparency.

Ken Hinds, of Haringey Stop and Search Monitoring Group, said he had been stopped by officers more than 120 times in the past 30 years, accusing officers of using racial profiling.

The Metropolitan Police have pledged to sign up to a new voluntary code of conduct for all police forces on stop and search, which will see data published on all outcomes from uses of the new powers.

The changes are being brought in after Her Majesty's Inspectorate of Constabulary (HMIC) found that 27% of stop and searches did not contain reasonable grounds for suspicion, meaning that more than 250,000 of the one million searches carried out last year could have been illegal.

In addition, black and minority ethnic (BME) members of the public were up to six times more likely to be searched than white people.

But Mr Hinds, speaking on the BBC Radio 4 Today programme, said he did not think reforms would be effective.

He said: "I believe after 40 years of abuse of stop and search - we now refer to it as stop and scarred in our community - what's happened is it has alienated whole swathes of communities.

"They cleverly keep saying stop and search is used for getting knives and guns off our streets. If that's the case, why is it, out of 1.2 million stops that you have, only 6% is used to target weapons?

"Come on... we have 40 years of scarring and I'm saying you cannot expect communities affected by it to say OK."

Speaking on the same programme, Chief Constable Alex Marshall, of the College of Policing, defended the powers.

He said: "Stop and search is a really important power to protect local communities from people carrying weapons, who are carrying stolen property, from drug dealers moving their drugs about.

"But in many cases, the person stopped and searched does not have anything on them and that stop and search must be carried out with respect and courtesy.

"Then the evidence shows people will support the use of stop and search if it is well targeted and is carried out with respect."

Mr Marshall said a black man driving an expensive car would not be reasonable grounds to carry out a search - despite Mr Hinds' reports of his own experience.

The Chief Constable said the new data published under the code of conduct would set standards of policing and help to redesign training.

Home Secretary Theresa May announced the Best Use Of Stop And Search Code Of Conduct after admitting that the power had been misused in the past.

Under the scheme, police forces who sign up voluntarily will agree to more limits on blanket Section 60 stops, used on the anticipation of serious violence without suspicion that a person is carrying weapons, while better records will be kept of each instance and published online.

The Met said it was introducing those two elements of the new plan from today and comes after Section 60 searches were used as a tactic in combating violent crime at this year's Notting Hill Carnival.

Last year 47,141 arrests were made as a result of stop and search, representing 20% of total arrests by the Met, and, of the 251,161 people who were stopped and searched from August 2013 to July 2014, 115,270 (46%) were white, 72,016 (29%) were black and 34,267 (14%) were Asian. Men accounted for 94% of all searches.

Commander Adrian Hanstock, the Met's lead for stop and search, said in a statement: "The Met has made significant improvements to stop and search over the last two years to not only reduce the total number of people we search, but also to ensure that our officers focus on those areas and types of crime that the public are most concerned about.

"As a result, we are arresting more people than ever before following the more targeted use of stop and search and routinely find people in possession of weapons and stolen items.

"In line with the Best Use Of Stop And Search scheme and our commitment to increase transparency and accountability, the MPS has today introduced a new approach to Section 60 authorisation and has introduced revised recording of stop and search outcomes."

Speaking in the House of Commons when announcing the shake-up in April, Mrs May said misuse of the power damaged public trust in the police.

She said: "While it is undoubtedly an important police power, when it is misused stop and search can be counter-productive.

"First, it can be an enormous waste of police time. Second, when innocent people are stopped and searched for no good reason, it is hugely damaging to the relationship between the police and the public. In those circumstances it is an unacceptable affront to justice."