Heavy-handed police bureaucracy is unfairly targeting and discriminating against the urban music scene, according to agents, the body which represents the industry, and MPs.

At a recent major urban event at a mainstream live venue, organisers say that police insisted on searching 18 performers for weapons before they went on stage, as well as a group of young people on work experience organised by a charity.

The Metropolitan police's risk assessment of live urban music gigs is based on the ethnicity of the audience and artists, according to industry figures. Police can ask for strict safety measures to be put in place on the basis of this risk assessment, and can cancel gigs at short notice.

At the event, police told organisers they had intelligence about an artist on the bill, but would not specify which one, saying they all needed to be searched. An airport-style scanner was used to check the artists and anyone else involved in the gig each time they entered the venue, the event's booking agent said, speaking on condition of anonymity.

"Of course we complied, we can't afford to rock the boat, but it is definitely racist, it is definitely not fair," he said. "The problem is that it reverberates through young people, they go to different types of events, they see that at indie events they are not treated like this. It just antagonises them." He added that booking agents and promoters were often unwilling to speak out about the issue because of fears they would be targeted by police, or that venues would be less willing to book artists.

"It's dangerous territory. If artists complain about it then it could be even worse for them. We all need to earn a living, and at the moment it is not a level playing field. Basically we have to keep our mouths shut and toe the line," he said.

Last year a cultural event organised by London youth arts charity A New Direction aimed at young people, featuring Bhangra drummers and a 14-year-old talent contest winner, was informed the day before the show that extra security would be required or the event could be cancelled. The resulting cost took the event over budget and two police vans were deployed outside the event, before being asked to leave.

Edna Pletchetero, one of the event's organisers, said: "This was a very positive event and we have never had any trouble before. Additional security did cost us more money and whether that's right or wrong, that's what happened. The additional police presence created a different atmosphere to the kind of event we envisioned putting on."

Sarah McKinley, founder of Xtreme Talent Artist Agency, an urban booking agency, said the risk assessment, using form 696, was not being conducted sensibly. "Often the risk assessment happens after the night has been advertised. People have already spent money and then the night can get pulled."

She added that it was a problem for artists who may have had problems with the law in the past, who wanted to change their lives. "The police think these artists are doing gigs for fun, but it's a living, it's the way they support their families," she said. Artists were unfairly stigmatised if there was trouble in the audience at an event. "If a fight breaks out it could then mean next time the DJ may fail the 696 form. It causes a stigma against that DJ and then people are scared to book them."She added that in her view, the 696 form was only used for urban artists, so was discriminatory. "I've never known a club to have to do a 696 for a normal, non-black event."

The form was having a damaging effect on the urban scene, she said. "It's a waste of time and clubs are more wary of putting on urban artists which makes my job more difficult."

John Whittingdale, who chairs the culture, media and sport committee in the House of Commons, said he continued to call for the "discriminatory and draconian" form to be scrapped, after his committee first demanded its abolition in 2009.

"We looked at it and were of the view that form 696 was discriminatory and completely unnecessary. It appears that problem still exists and it is still being used by the Met to target particular types of music."

Jo Dipple, acting chief executive of UK Music, the UK music industry body, said: "We have seen no evidence that directly links music, never mind artists and musicians, with crime and disorder."

Police say that following "concerns" the form had been modified to remove "any reference to music genre".

But the current form, which asks for details about events "that predominantly feature DJs or MCs performing to a recorded backing track", clearly targeted urban artists, said Dipple.

"This is unacceptable. Performers being searched goes way beyond the stated guidance of this supposedly voluntary process," she said, arguing that police were hampering one of the UK's successful music exports, which has seen artists like Dizzee Rascal and Ms Dynamite achieve international success.

In a statement the Met said the form was a "voluntary risk assessment form", but the current form recognised that it may be "a licence condition on some premises licence", in which case it would be "mandatory".

A spokeswoman said that form 696 was "intended to identify where an event might be at risk from crime and take steps to prevent it.

"To date shootings linked to licensed premises have been significantly reduced and we believe the risk assessment process has contributed to this."