The focus on the needs of a “mystical” white working class in the aftermath of the Brexit vote has led politicians to neglect the needs of a growing ethnic minority population across the north of England, the authors of a report warned on Thursday.

Researchers behind the paper by the Runnymede Trust and the University of Leeds said that “deep racial and ethnic inequalities” were not being adequately addressed by existing plans to boost economic growth in the region, such as the “northern powerhouse”. And they argued that most discussions of the northern working class in the media and political debates since Brexit had left out minority groups who have lived in the region for decades.

“Ethnic minorities have been part of working class communities in the north since postwar migration,” said co-author Omar Khan, director of the Runnymede Trust. “They should not be forgotten or ignored in current political and media coverage of ‘working class communities’.”

Narratives focusing on a disaffected white working class in post-industrial northern towns risk treating the north as a “monolithic area”, the report argues, and also ignores areas where diversity has increased due to newly arrived European migrants and asylum seekers.

Some northern cities now have among the largest ethnic minority populations in the UK, rising by 74% in the north-east, 69% in the north-west and 68% in Yorkshire and Humber. These new migrant groups groups are all more likely to be working class than not.

The report argues that some local authorities are failing in their statutory duties under the Equality Act if they fail to address discrepancies between various ethnic groups.

This may lead to economic proposals ignoring the discrimination faced in education, the workplace and in relation to home ownership by ethnic minority groups, the authors suggest.

Dr Roxana Barbulescu, who leads the Commission on Diversity in the North project with Prof Adrian Favell at the University of Leeds, said that while racial inequalities are “a feature of modern Britain”, they run deeper in the north of England.

She added: “The north is not a monolithic area and there is remarkable variation between cities and towns.

“Future plans for regeneration of northern cities and towns have to reflect and cater to their racially diverse population.

“The government has taken a step in the right direction with the introduction of a national Racial Disparity Audit but this should be followed by investment in the areas with the highest inequalities to uphold the commitments taking place under the Equality Act and they have to be articulated within wider policy agenda such as the Industrial Strategy.”

Favell said that the northern powerhouse agenda has “very little space for ethnic or racial diversity” and “very little thinking about these places that are not cosmopolitan like Manchester or Leeds”.

He pointed out that towns that were predominantly white that had experienced a rapidly changing demographic would need a different political approach to towns with an established BAME population.

The report highlighted the increase in hate crimes, with the north of England accounting for around a third of all hate crime taking place in England and Wales. Last year, nearly 29,000 reported incidents of hate crime took place in the region, an increase of around 6,000 from 2017.

Khan said: “This briefing highlights that many towns and cities in the north of England are ethnically and racially diverse.

“The racial inequalities that BAME groups and people experience – for example in education and employment – should be tackled as part of any national or regional economic growth agendas, including those proposed by mayors.”