A MISSING mother from Basildon may have “gone underground” with her three-year-old son, lawyers say.

Ellie Yarrow-Sanders has not used her bank accounts or mobile since disappearing with Olly Sheridan six months ago, according to solicitors representing the youngster's father, Patrick Sheridan.

Staff at law firm Irwin Mitchell on Thursday renewed appeals for help finding Olly and his 26-year-old mother and said the situation was becoming "increasingly serious".

Olly is at the centre of a family court dispute between his estranged parents.

Miss Yarrow-Sanders disappeared with Olly in July a few weeks before she was due to give evidence in a "critical" family court hearing, lawyers say.

A judge raised the alarm in December and urged anyone with information to come forward.

Mr Justice Williams, who had overseen a hearing in the Family Division of the High Court in London, said he was gravely concerned.

Family court hearings have been staged in private and journalists had been barred from identifying any involved family members, who come from Basildon.

But Mr Justice Williams said he was lifting the identity bar in the hope that publicity would help find Olly and Miss Yarrow-Sanders.

READ MORE: Father of vanished three-year-old from Basildon is 'sick with worry'

He said they could be named and photographs published.

Essex Police are also searching and have urged anyone with information to get in touch.

An Irwin Mitchell spokesman said on Thursday: "Ellie has gone underground since abducting Olly.

"She has not used her bank accounts or mobile phone since she and Olly disappeared in July."

The spokesman said Miss Yarrow-Sanders' mother had travelled to Huddersfield, West Yorkshire, at around the time Olly vanished.

She said Miss Yarrow-Sanders' and Olly might also have stayed in the Huddersfield area.

Lawyer Jenna Lucas added: "The situation for Olly Sheridan is increasingly serious."

Mr Sheridan, 45, said Christmas had been "unbearable".

He said: "I hope that Ellie sees sense and comes forward so that this can be sorted out and Olly can have a normal childhood, not living on the run.

"My boy needs both of his parents in his life and not to live a life undercover, hidden away from his family and the rest of the world.

“If any members of the public who might have seen Olly or have any information, call the police."