Victims of historic child abuse are to demand answers about the independence of a public inquiry into the problem, at a showdown meeting with Deputy First Minister John Swinney.

Alan Draper, spokesman for In Care Abuse Survivors Scotland (INCAS), said Mr Swinney would need to answer questions about the allegations made by both Professor Michael Lamb, who quit the inquiry panel last week, and Susan O'Brien QC, who left while under investigation for allegedly holding views 'incompatible' with the post of chair of the Scottish Child Abuse Inquiry.

READ MORE: War of words as QC leading abuse inquiry is forced out claiming she was 'undermined'

Mr Draper said: "Professor Lamb has made some serious allegations about government interference in the work of the inquiry. We assume that the government is not questioning his integrity. We need,therefore, to know in what way the government interfered, why they interfered, and who authorised the interference?

"These are crucial questions. Survivors need honest answers from government , if their trust in the process is to be restored."

READ MORE: War of words as QC leading abuse inquiry is forced out claiming she was 'undermined'

Mr Draper said Ms O'Brien's position also needed clarification: "We understand that Susan O Brien has resigned or has been pushed by government. We require a detailed account of the events that have taken place and a full explanation of the views that were considered unacceptable."

The head-to-head meeting was already arranged before the shock resignations of the past week.

Professor Lamb left citing government interference in the supposedly independent work of the committee, which he said left it "doomed". Ms O'Brien, in her resignation letter to Mr Swinney said she agreed with him.

READ MORE: War of words as QC leading abuse inquiry is forced out claiming she was 'undermined'

The Scottish Government insists the inquiry remains independent and will continue its work while a new chair and panel member are appointed.

However the position of the inquiry itself and its remaining panel member, former Northern Ireland social care regulator Glenn Houston remains unclear.

A spokesman for the Scottish Child Abuse Inquiry last night insisted: "The Inquiry has been, and continues to be, independent of the Scottish Government."

But a concern raised by all three of the original panel, Ms O'Brien, Prof Lamb and Mr Houston remains unaddressed.

They had objected to a Scottish Government official sitting in on all their deliberations, but Ms O'Brien said a proposal to hire a solicitor to fill the role had been rejected.

In her resignation letter to Mr Swinney, Ms O'Brien said that in June this year "the panel's formal request fro a decision from you which would enable it to bring in an outside solicitor to replace a Scottish Government employee has been blocked."

The Scottish Government claims said this was not the case. A spokeswoman said: “There was no request to remove staff, but rather fill a vacancy.

"The request was for the vacancy to be filled, on a part time basis charged at £340 an hour. We confirmed, most recently on 21 June, that we were considering the request and would respond in due course.”

An update on the cost of the inquiry is expected shortly but it had cost £610,000 by December of last year, and this had almost doubled to £1,113,817 by March 2016.

Because she resigned, Susan O'Brien will not receive a pay-off, but had served for almost exactly a year after being appointed on July 1 2015, and is likely to have received close to the maximum of £262,500 allowed under her contract during that time.

Mr Swinney is plainly concerned about the rising cost of the inquiry and has queried whether evidence taken from victims could have been heard by junior counsel costing less than the £100 a day paid to senior counsel who have so far been used. He said any involvement from Scottish Government officials was limited to ensuring costs were appropriate, with the inquiry independent "in every other respect".

However the latest developments have left many survivors dismayed and highly suspicious of the motives behind the Government's attempts to remove Ms O'Brien.

Helen Holland, a member of In Care Abuse Survivors Scotland said: "The cost of lawyers so far has been for the elderly, sick and housebound who wanted their testimonies recorded, poor souls."

Ms Holland has been supporting such victims - who may not live long enough to know the inquiry's results, and the more expensive lawyers had been necessary because the inquiry was at an early stage, she said.

"Mr Swinney is misleading people. These are exceptional cases because the team was not fully set up yet," she said. "We are seen as a financial burden, just as a lot of us were as children. He is saying we only deserve the cheapest possible scraps. It is disgusting, and more offensive than anything Susan O'Brien may have said".

She claimed publishing details of an investigation into Ms O'Brien was a smokescreen, adding: "They are trying to take the focus away from the core of the matter, which is government interference."

The Scottish government continues to strongly reject claims that the work of the inquiry has been interfered with, says Mr Swinney will reassure survivors about this when he meets with them on Thursday.