THE man who warned the SNP about wife-beater Bill Walker's violent past has called for party chief executive Peter Murrell to consider his position.

Rob Armstrong, who gave the Nationalists an affidavit written by Walker in which he admitted striking his former step-daughter, said Murrell should take responsibility for the SNP's failure to act earlier.

Murrell is married to Deputy First Minister Nicola Sturgeon.

Walker's conviction last week on 23 assault charges has prompted questions about why he was selected by the SNP as the party candidate for Dunfermline in 2011.

The Sunday Herald revealed last year that Armstrong, the former brother-in-law of Walker's third wife, Diana, warned the SNP in 2008.

He met one of Sturgeon's aides in her constituency office and presented documents about Walker's past. Party headquarters, led by Murrell, was informed and an investigation was launched.

However, no action was taken and Walker was selected as a Holyrood candidate.

Armstrong told the Sunday Herald last week: "Peter Murrell was the chief executive of the SNP at the time I handed over information to the SNP. He should consider this position.

"There has to be an investigation into why my approach to the SNP was treated so negligently."

The retired pilot said he recalled showing Sturgeon's aide at least three documents: a ­hand-written affidavit by Walker about a child access case; an old newspaper cutting about his past; and a damning court judgment.

In the 1987 affidavit, Walker wrote about an incident in which he hit his former step-daughter Louise with a saucepan.

Walker also responded to Louise's claim that he smacked her on the bare bottom until the age of 15.

He wrote: "After no more than [waiting] 15 minutes she did receive her 'punishment', one smack on each buttock with a slipper, with her navy blue knickers on."

Armstrong said he also handed over a 1991 newspaper article, which focused on a child custody battle.

The opening paragraph stated: "This is William Walker, a child disciplinarian who has admitted hitting his wife. He has been described as a bully and a tyrant by a judge. He has admitted hitting his step-daughter with a saucepan."

Sturgeon and First Minister Alex Salmond said last week that they had been unaware of the information provided by Armstrong.

She added that SNP headquarters had investigated the claims: "As my staff are not employed by the SNP, these matters are quite rightly passed on to the party. The member of staff who spoke to Mr Armstrong acted absolutely appropriately.

"The investigation conducted by a member of staff at SNP HQ did not find any evidence of any complaint in law or legal proceedings into domestic violence by Mr Walker, and the inquiry was then closed."

Labour MSP Claire Baker said: "Mr Armstrong deserves an apology from the SNP for their conduct in this whole situation and he is quite right in calling for action now.

"We need to know what the leadership knew, when and who made the decision to allow Walker to become a candidate despite these serious allegations. I agree with Mr Armstrong that Peter Murrell must consider his position in light of this."