The response from Police Scotland’s chief constable to the new investigation into the murder of Nairn banker Alistair Wilson fell below expected standards, Douglas Ross has said.

The Scottish Conservative leader raised the Wilson family’s concerns at First Minister’s Questions on Thursday, after they described Chief Constable Jo Farrell as “callous” following comments in which she said she has no plans to meet them.

First Minister John Swinney said he cannot comment on a live investigation but he did voice “deep concern” that the murder of Mr Wilson remains unsolved after 20 years.

The 30-year-old father-of-two was shot on his doorstep in November 2004 and his killer has never been found.

Scotland’s top law officer, the Lord Advocate, last week ordered a complete reinvestigation of the case.

Ms Farrell was asked about it when she spoke to journalists on Monday, saying she is “absolutely committed” to getting justice for the Wilson family and that it is important for the new senior investigating officer to build a relationship with them.

In the Scottish Parliament on Thursday, Mr Ross referred to comments from Mr Wilson’s son Andrew, who has complained the family are being “kept in the dark”.

Mr Ross said the family are “still grieving the loss in horrific circumstances”, adding: “The response from Police Scotland following the decision by the Lord Advocate is one that clearly falls below any standard we should expect, particularly from the chief constable of Police Scotland.

“The chief constable is being described by a grieving family as callous.

“I hope the First Minister will reflect on that and seek to address what could happen.”

Mr Swinney said he shares the family’s frustration that the case remains unsolved, noting that police and prosecutors operate independently of Government.

He said: “I do not want in any way to create any sense that I am not sympathetic and empathetic to the situation in which the Wilson family found themselves.

“Alistair Wilson was murdered on his own doorstep, his killer or killers have not yet been brought to justice, and that deeply concerns me.”

He said police have had “formidable success” in resolving historic murder cases using modern investigative techniques.

In order to preserve the “constitutional separation of responsibility”, the First Minister said he could not comment on Police Scotland’s operational matters.

Ms Farrell said on Monday that a new senior investigating officer has been appointed.

A Police Scotland spokesperson said: “The chief constable was referencing the strategic senior investigating officer, Detective Chief Superintendent Suzanne Chow, who was in contact with the family last week via family liaison officers.

“A senior investigating officer has also been appointed and the wider team which will take forward the reinvestigation is being identified.

“The family have been kept updated on this work.”