Broadly speaking, the fallout from the
Rotherham child sexual exploitation scandal, in which hundreds of teenage girls have been sexually assaulted by grooming gangs, primarily of Pakistani immigrants. It's a major scandal in the UK because the response of the police and government has been less than effective, to say the least.
The Rape Gang Inquiry Report referred to is an independent report by MP Rupert Lowe, which further alleges that 250,000 British teens are victims of grooming gangs, with 87% of the offences committed by Pakistanis.
It's important to note that the Lowe report is unofficial, and that 250K number is an extrapolation. The Jay inquiry in 2014 concluded that there were an estimated 1,400 victims of child sexual exploitation in Rotherham, some as young as 11. 250,000 is 20 times that--fully two orders of magnitude. If you feel that number seems "off," use discernment. The problem with the rape gangs is real, as is the government's failure to deal with the crisis; the magnitude of it is not known with certainty.