A MUM yesterday urged cops to quiz a jailed killer she believes has the key to finding her son and Madeleine McCann.

Charles O'Neill is said to have been in Portugal when Maddie, three, was snatched in 2007.  

Two months earlier he was in Gran Canaria, in Spain's Canary Islands, when Jeremy Vargas, seven, vanished.

Jeremy's mum Ithaisa Suarez, 27, said: "I believe he might know where they are, or what happened to them.

"They're identical cases. Children who vanished in minutes, leaving no trace. He's a vile monster and should be questioned again." O'Neill, 47, and his gay lover William Lauchlan were jailed for life last Thursday for murdering mum-of-three Allison McGarrigle in Largs, Ayrshire - to stop her exposing them for child abuse.

The pair had earlier done time for drugging and abusing youngsters. O'Neill has refused to meet detectives working for Maddie's parents Kate and Gerry McCann.

Ithaisa said: "He was interviewed by police looking for Jeremy. They found no evidence. But if he didn't do it, he may know who did."

She said Spanish police told her they believe Maddie and Jeremy may have been targets of the same gang.

All over Gran Canaria there are billboards and posters bearing Jeremy's picture and a telephone number to ring with information.

Ithaisa is appealing to Brits going on holiday there to look at his photo before they arrive so they can help find him. An age progression picture, like the one depicting how Maddie could look aged six, is also being created.

Ithaisa said: "Please, please remember my son. Please keep an eye out for him while you are here. Please look for him. We need your help. Remember Jeremy and Maddie, we need to get them home."

Ithaisa is in regular contact with Kate, of Rothley, Leics. She said: "Like Kate I will never give up looking." a.lazzeri@the-sun.co.uk