A confidential file of letters from Scottish bishops detailing more than 20 secret abuse cases has been handed to police by a former safeguarding adviser to the Catholic church.

The intervention by Alan Draper, a former adviser to the Motherwell diocese, comes as the church attempts to draw a line under unfolding sex-abuse scandals by announcing a series of measures to be read at all masses this weekend on behalf of the Scottish bishops. However, describing the initiatives as a "charade", Draper says it is time for criminal investigations and an independent Scottish government inquiry into sexual abuse in the church.

The letters, dating back to 1995, include every Scottish diocese. One bishop, who describes abuse against "two severely mentally-handicapped young female adults", asks Draper to destroy his letter after reading it. Another refers to an abused child as a "young female parishioner". while a 15-year-old boy is described as "sexually mature".

A Catholic media spokesman, Peter Kearney, said the church would co-operate fully with the police, but added: "If someone has been in possession of material which they felt showed criminal behaviour, they would be expected to explain why they had taken 18 years to hand it to the authorities."

"The letters were given to me in confidence, and for a long time I respected that," explains Draper. "But the church has failed to reach out to victims and I have felt increasingly frustrated with their inability to manage the situation. It's a matter of public interest that the file be revealed."

Draper, a former deputy director of social work and a retired senior lecturer in medical ethics, says that both the tone and substance of this weekend's church statement on abuse confirmed his conviction that he should release the file: "It's pious words. It says the church recognises the trauma and pain of survivors. How are they doing that? Where's the evidence of justice and healing? They talk about supporting those who have been harmed. Where's the support? If anyone attempts to sue the church, the attitude turns adversarial and the lawyers and insurance people say no."

The statement outlines three initiatives: the publication of a diocesan safeguarding audit between 2006 and 2012; an external review of safeguarding procedures by the Very Rev Andrew McLellan, former moderator of the General Assembly of the Church of Scotland and a former chief inspector of prisons; and a statistical review of all historic cases of abuse from 1947 to 2005.

"It's all statistics," says Draper. "It's not a forensic audit which would open up their files and look at cases. Most of it is to be done by appointees of the diocese who rely on the patronage of the bishop. The 'independent' bit is being done by Andrew McLellan and, while I'm sure he's a fine human being, how is he qualified? It should be conducted by three experts in the field, whose independence and integrity are beyond reproach."

The statement insists that McLellan's review will "be seen as an endorsement of our safeguarding service".

Kearney insists that the historic audit will look at how cases were dealt with and says McLellan is "an eminent and respected figure with an exemplary record of public service".

However, the bishops' statement has ignited debate about the gulf between the church's public statements and private actions.

"It's only words," says Father Gerry Magee of St Winin's in Kilwinning, Ayrshire. "Nothing is being done. I have an abuse victim in my parish and, despite being publicly named, not one person has contacted him." Another Scottish priest said: "It's disgraceful. Nowhere in that statement is the word 'sorry' used."

In August, Hugh Gilbert, bishop of Aberdeen, made a public apology for abuse suffered at Fort Augustus boarding school, saying: "We are anxious … that all that can be done should be done for victims."

Last month he wrote to David Greenwood, the solicitor for a Fort Augustus abuse victim, Andrew Lavery, saying: "The diocese of Aberdeen has no liability." In a stinging rebuke, Greenwood replied: "The tone of your letter … illustrates the callous nature in which the bishops of Scotland have treated victims of sexual abuse by their priests."

Survivors are still concerned by the lack of care and transparency in the church's approach. Pat McEwan, whose abuse case was highlighted by the Observer, received a letter from the church's national safeguarding co-ordinator, Tina Campbell, criticising him for talking to the media.

Last month, James McDermott wrote to the newly-appointed Archbishop of St Andrews and Edinburgh, Leo Cushley, about abuse he suffered while at Sacred Heart primary school in Glasgow. Cushley's assistant replied: "While the archbishop sympathises with your situation, he regrets that he is unable to assist you."

"New face, same old song," says McDermott.

Draper says that this "un-Christian attitude" contrasts with the church's traditional protection of abusers, who have been given therapy and financial assistance, adding: "The latest statement makes no mention of assessing what support has been provided to survivors. It is window dressing yet again. They have learned nothing."