An urgent search is underway to find a mum who vanished seven months ago with her four-year-old son.

Sarah Elizabeth Tate, 38, and youngster Thomas Alexander Bakyrey have not been seen since November 2018.

The pair from Adelaide in Australia are believed to be hiding somewhere hundreds of miles away in Victoria.

Now police have launched a national search to track them down, with an arrest warrant being issued for the fugitive mum.

The boy’s father, Sergiy Fedirovich Bakyrey, 36, told The Advertiser   that they went missing while he was away working.

He said: “I am very worried about Thomas’ welfare as his disappearance was without any warning and I do not know where he is.

A warrant has been issued for the arrest of Sarah Elizabeth Tate

“I know Thomas was very much looking forward to seeing me...and that he will be distressed about where I am and why he has been taken away from his home.”

Extensive searches to find the pair have so far been unsuccessful and fears are growing for Thomas' welfare.

Ms Tate’s last posts on social media accounts were in January and she has also lost touch with her immediate family.

Shortly before the pair disappeared, she texted Mr Bakyrey about their son's upcoming birthday but failed to “mention that she was leaving with him”, he added.

The mum has not been active on social media since the start of the year

A judge has authorised Australian Federal Police, state police forces or a court Marshal to “recover the child” and return him to his father.

Ms Tate's white, 2017 Toyota Rav 4 with South Australian registration S785BXR was last seen at Bordertown, South Australia, in late February.

A police spokesman said: "The pain of a missing child is incomparable. We can only imagine what Sergiy and the rest of Thomas' family are currently going through.

“If you see Thomas or Sarah, or have any information on their whereabouts, we urge you to contact (police) and help reunite Thomas with his family.

Ms Tate’s car was last seen at Bordertown in late February

"Hiding a child from their families can have adverse effects and the AFP strongly urges the return of Thomas to his home in Adelaide."

Ms Tate is described as having long brown hair, which is sometimes dyed in shades of red.

She wears glasses and is around 163cms tall and of a small build.

Thomas has a slim build, blue eyes and light brown hair.