More than 2,800 so-called honour attacks -- punishments for bringing shame on the family -- were recorded by Britain's police last year, according to figures released on Saturday.
At least 2,823 incidents of "honour-based" violence took place, with the highest number recorded in London, the Iranian and Kurdish Women's Rights Organisation (IKWRO) found.
The figures were compiled from 39 out of the 52 British police forces. The others were unwilling or unable to provide data. Eight areas recorded at least 100 incidents, the figures showed.
The attacks included murder, mutilation, beatings, abduction and acid attacks.
Compared with 2009 figures released by 12 police forces, there was a 47 percent rise in incidents.
The Metropolitan Police (London) recorded 495 attacks; West Midlands (Birmingham) 278; West Yorkshire (Leeds, Bradford) 350; Lancashire (northwst England) 227; Greater Manchester 189.
"This is the first time that a national estimate has been provided in relation to reporting of honour-based violence," the report concluded.
"The number of incidents is significant, particularly when we consider the high levels of abuse that victims suffer before they seek help."
IKWRO director Diana Nammi told the BBC: "The perpetrators will be even considered as a hero within the community because he is the one defending the family and community's honour and reputation."
Honour crimes mostly happen in South Asian, eastern European and Middle Eastern communities, she said.
Honour-based violence is an "organised or collective crime or incident" orchestrated by a family or within a community, she said, adding: "It can be by a relative and sometimes on the order of community members."
Things considered dishonourable include having a boyfriend, being a rape victim, refusing an arranged marriage, being gay and in some cases wearing make-up or inappropriate dress.
IKWRO believes the British government does not have a proper national strategy to deal with honour-based violence.
Though it believes awareness of the issue has increased in recent years, police, teachers, social workers and other professionals "still don't really understand it".
A spokesman for the Home Office interior ministry said: "We are determined to end honour violence and recognise the need for greater consistency on the ground to stop this indefensible practice.
"Our action plan to end violence against women and girls sets out our approach to raise awareness, enhance training for police and prosecutors and better support victims."
Widely-reported honour crimes have shocked Britain, a nation widely deemed to have successfully absorbed immigrant communities and customs.