By Michael Holden

LONDON (Reuters) - Dying British lawmaker Jo Cox pleaded with her aides to save themselves after her killer launched a frenzied attack, prompting him to return to carry on the deadly assault, a court heard on Wednesday.

Labour Member of Parliament Cox, a 41-year-old mother of two young children, was shot three times and repeatedly stabbed on the street in the town of Birstall, part of her electoral district in northern England, as she arrived for an advice session with local residents at a library.

Thomas Mair, 53, who lives locally, denies her murder.

Two aides with her at the time, her manager Fazila Aswat and senior caseworker Sandra Major, told the Old Bailey court how her killer had launched a second ferocious attack after she survived his initial assault.

"At that instant our lives changed forever," Aswat said as she recalled the attack which occurred a week before Britain's Brexit referendum in June in which Cox had been a strong supporter of remaining in the European Union.

Major said the man approached Cox and shot her in the head. She fell to the ground with blood running down her face.

"Jo was lying on the floor and she sort of tried to sit up a little bit. He just started stabbing her while she was lying on the floor," she told the jurors.

The aides screamed at the man to get away, saying she had two little children. Cox rolled off the pavement into the road and the man approached Major and Aswat waving his knife.

"HE CAME BACK"

"She shouted 'get away, get away you two, let him hurt me, don't let him hurt you,'" Major told the jury. "He started to walk away a little bit. When Jo shouted out he came back. He shot her twice more and started stabbing her again. She was on the floor, she didn't get up again."

Prosecutors said on Monday Mair had researched white supremacists, Nazi Germany, shootings and assassinations before the attack.[L8N1DF20M]

Major said the attacker had shouted out something like "Keep Britain independent" or "British independence" while Aswat recalled: "he said 'Britain first, this is for Britain, Britain will always come first.'"

Bernard Carter-Kenny, now 78, was waiting for his wife outside the library when he saw he heard the gunshot and saw a man stabbing Cox. He rushed to help.

"I thought if I can jump onto the back of him I could take him down," he said in a statement read to court. However, the man turned and stabbed him in the stomach and he was forced to retreat to a nearby shop.

Jurors also heard that in a holdall he was carrying at the time of his arrest there was a leaflet relating to the referendum from the "Stronger in Europe" campaign.

The trial continues.

(editing by Stephen Addison)