Deputy Children's Commissioner, Sue Berelowitz, has told Daybreak that her report into child sexual exploitation "is a wake-up call."
She added: "We are saying to government, to local authorities and police forces, you have to take this very seriously ."
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An Opposition MP says the PM should address claims relating to the allocation of public funds when he was London mayor.
Harry will also pay tribute to a British soldier killed by an elephant during anti-poaching operations in Malawi.
The family are making an official visit to South Africa.