SNP policies are targeted at helping the middle classes rather than the poorest in society, the leader of the Scottish Liberal Democrats has said.

Willie Rennie spoke out after it emerged that Naomi Eisenstadt, Nicola Sturgeon's poverty tsar, had questioned the Scottish Government's approach to some universal perks in a private note to the First Minister.

The document, the release of which under Freedom of Information laws was originally blocked by SNP ministers but made public after the decision was appealed, reveals that she queried the cost of spending cash on "those who could fund themselves" and whether the better-off enjoyed a disproportionate share of services.

She asked for the First Minister's views on what she described as "policy tensions" around some initiatives such as free tuition fees and childcare, which she said could come at the expense of investment in non-academic training and quality of provision in early years education.

Mr Rennie said: "It is no wonder they tried to prevent the release of this report. The verdict from the experts is in. The SNP talk about helping the poorest in society but their policies are targeted at the middle classes. The First Minister has the powers she needs to reduce the burden on people struggling to get by but her rhetoric has not been matched by her actions."

Ms Eisenstadt, ahead of a meeting with the SNP leader in late August, also expressed surprise and concern at the number of people classed as poor in Scotland. Her research found almost one in five Scots was classed as "poor" after housing costs, with 625,000 in severe relative poverty, a substantial proportion of whom were in work.

She also informed the First Minister that pensioners were the group least at risk of poverty in Scotland, although this did not prevent the SNP administration from ruling out withdrawing winter fuel payments from wealthy pensioners and instead spending the cash on supporting those most at risk of poverty, such as lone parents, single, working age adults and those in private rented housing.

Patrick Harvie, the co-convenor of the Scottish Greens, said there remained a strong case for universalism in public services, based on the need to show that everyone is part of society rather than "fostering division and resentment between those who pay in and those who receive services".

He added: "The wealthy should of course pay a greater share to fund the services our society needs. With the range of existing powers and those in line to be devolved Holyrood will be better able to achieve that, and close the inequality gap without endangering the universal services which make our society better and fairer precisely because we provide them collectively."

John Dickie, Director of Child Poverty Action Group in Scotland, also backed universal entitlements such as child benefit and free school meals, which Ms Eisenstadt did not mention in her note, and argued that taxation should be used to ensure everyone received the support they needed.

He added: "A progressive approach to taxation can ensure that collectively we all pay according to our means for the benefits and services that help prevent poverty and ensure all our children get the best possible start in life."

The Scottish Government has said that a poverty advisor was appointed as part of its commitment to tackling inequalities and building a fairer country. A spokeswoman added that Ms Eisenstadt had been asked to be "frank and honest" and that the Government was looking forward to the release of her report in the new year.