Reward offered for Aisling

British billionaire Lord Michael Ashcroft has offered a $50,000 reward for information leading to a conviction in the Aisling Symes case.

Today marks one week since the two-year-old vanished from Longburn Rd in the West Auckland suburb of Henderson.

Lord Ashcroft, the founder of the anonymous tipline Crimestoppers United Kingdom, announced the reward at the unveiling of Crimestoppers New Zealand in Manukau today.

Lord Ashcroft established the Crimestoppers line in Britain in 1998, leading to more than 80,000 arrests in that country, paying rewards in some cases.

His $200,000 reward led to the return of 96 war medals stolen from Waiouru Army Museum in 2007.

"We are grateful yet again to Lord Ashcroft for generously providing a reward which leads to the successful apprehension and conviction of the perpetrator of Aisling's disappearance," Crimestoppers NZ chairman John Perham said today.

Meanwhile, the search for Aisling continues with police calling for anyone who had information to come forward.

Detective Inspector Gary Davey said he was still hopeful someone had abducted her and was looking after her, but could not rule out other possibilities.

Police had "nothing solid" in the search for Aisling and all they could do was follow the potential leads they had and "make sure we keep an open mind and follow each of those phases down to its conclusion", he said.

"We are still appealing for anyone who has her to come forward. We just want her back."

Aisling was last seen talking to an Asian woman walking a dog on Longburn Rd, about 5.30pm last Monday.

The woman, who is described as being in her 30s, has not yet come forward and police believe she may be the key to finding Aisling.

"She doesn't need to fear the police. We just need to identify her and speak to her," Mr Davey said.

Police had scheduled a media conference in Henderson today over the investigation but cancelled it at short notice, giving little explanation as to why.