The girlfriend of Nathan Matthews, 28, who was charged with the murder of his his 16-year-old stepsister, Becky Watts, has also been charged jointly with her murder.

Shauna Hoare, 21, was also charged with perverting the course of justice, conspiracy to commit false imprisonment and preventing her lawful burial.

Nathan Matthews is now also charged with a string of further offences, Avon and Somerset Police have said, including perverting the course of justice, conspiracy to commit false imprisonment and preventing her lawful burial.

Avon and Somerset Police also said the pair had also been charged with possession of a prohibited weapon and four counts of making indecent images of children.

Matthews has also been charged with sexual assault and voyeurism. The alleged sexual offences do not relate to Becky.

The new charges will be added to the indictment at their next court appearance, which is a plea and case management hearing at Bristol Crown Court on 4 August.

Becky went missing from her family home in Crown Hill on 19 February and police launched a search on 20 February when she was reported missing.

Her body parts were found by police at a house in Barton Hill, Bristol, on 2 March and detectives charged Matthews with murder.

Hoare, of Cotton Mill Lane, Bristol, is still accused of intending to pervert the course of justice by lying to police.

There are no changes to the charges against Karl Demetrius, 29, Donovan Demetrius, 29, Jaydene Parsons, 23, and James Ireland, 23, who are all accused of helping dispose of and conceal Becky's body parts.

Detective Superintendent Liz Tunks said: "Our thoughts and sympathies are with Becky's family.

"This has been a very difficult time for them and they have had to endure yet more pain as we have worked to understand the full circumstances surrounding her death.

"Our continuing investigative work in this case demonstrates our determination to explore all avenues even after suspects have been charged.

Additional reporting PA