A British woman is among five people to appear in court in Kenya charged with stealing babies, embassy officials say.
The Church of England and doctors urged the Met to investigate
Miriam Nyeko and four others were in court as police investigated an alleged child-smuggling network between the UK and Kenya, the British embassy said.
The accused are said to be linked to the controversial UK-based evangelist Gilbert Deya, who has denied involvement in child trafficking.
His wife Mary Juma Deya, Mrs Nyeko and three others all deny the charges.
A British embassy spokesman said on Tuesday he had seen no evidence to support reports another of those accused, Rose Kiseram, is also British.
The case centres on claims by Mr Deya's London-based organisation, the Gilbert Deya Ministries, that previously infertile couples are able to conceive thanks to miracles inspired by prayer.
Church leaders and medical experts fear the "miracle babies" are simply victims of child trafficking.
The Kenyan authorities have taken 21 children - some only a few weeks old - into protective custody.
Ten were seized from the Nairobi home of the Deyas and 11 from the residence of co-accused Edda and Michael Odera, who on Monday also denied charges of stealing babies.
The BBC's Muchiri Kioi in Nairobi said Mrs Nyeko, a British citizen of Nigerian origin, had cradled one of the so-called miracle babies in her arms as she appeared before magistrates.
Mrs Nyeko, Mrs Deya and Ms Kiseram pleaded not guilty to abducting a baby girl from a hospital in Nairobi in February.
Ms Nyeko claims to have given birth to a boy named Daniel in Kenya last month, thanks to Mr Deya's help.
Her husband, Charles, a product designer who lives in London, said earlier this month it was a "miracle from God" they did not understand but for which they were grateful.
Kenyan authorities have insisted on DNA tests to establish the boy's parentage - and the British embassy has refused to grant him a passport until they happen.
Both the Church of England and the Royal College of Obstetrics and Gynaecology urged the Metropolitan Police to investigate claims involving members of the Gilbert Deya Ministries.
The church has 36,000 members in the UK, as well as branches in Europe, Africa and Asia.
All five defendants are due back in court on 3 November.