Blair Jenkins insisted union calls for greater social justice would "fall on more fertile ground" if Scotland left the UK.
The claims came as the pro-independence campaign group launched a report aimed at winning support from the trade union movement.
It was given a guarded welcome by the STUC but left-wing union activists dismissed Yes Scotland's case as "timid".
The Yes Scotland report – entitled Yes to a Just Scotland – is a response to the STUC's A Just Scotland document published last year, which called on both campaigns to set out policies promoting greater equality and social justice.
It avoids making specific policy proposals but suggests an independent Scotland would be more sympathetic to STUC demands for higher taxes on the wealthy, a more generous welfare system and stronger employment rights.
Asked ahead of the report's launch whether he believed independence would result in a more redistributive tax regime, Mr Jenkins replied: "Yes."
He added: "We believe the trade union movement will be able to deliver more of its agenda through Yes than No."
However, he declined to comment on the SNP Government's six-year council tax freeze and multimillion-pound "small business bonus" tax discount, which have been criticised by the unions.
In his introduction to the report, he admitted: "We do not claim the trade union movement will get all it argues for in an independent Scotland."
The report was launched in Glasgow by Mr Jenkins and actress Elaine C Smith in front of an audience of union members and charity representatives.
It asks the STUC to set out its own policies for an independent Scotland. It is understood that senior STUC figures urged the campaign group to tone down the highly political request during private discussions prior to the report's publication but were ignored.
STUC general secretary Graeme Smith said: "The STUC believes that significant challenges remain for both campaigns.
"Commitments in areas such as welfare continue to be made without the necessary related commitment to redistribution through increased taxation.
"Both campaigns lack any clear vision of how collective bargaining and a properly regulated labour market might be used to reduce income inequality."
Pauline Bryan, of the Red Paper Collective of trade union activists, said Yes Scotland's report was "timid".
She added: "Given the policy constraints of using a shared currency and the EU as envisaged by the Yes campaign, the document asks almost nothing which could not be answered by greater powers to a Scottish Parliament or ideally a federal arrangement within the UK."
Labour MSP Neil Findlay said: "To achieve social justice we need a progressive taxation policy to promote redistribution and the major player in the Yes campaign, the SNP, is opposed to this. On one hand the nationalists have tax exiles calling for tax cuts, and on the other they call for Scandinavian levels of public spending. Only last week John Swinney confirmed there would be no rises in personal taxation in an SNP-governed independent Scotland."
l The SNP has welcomed the launch of a new LGBT organisation, Out for Independence. The group is made up of lesbian, gay, bisexual and transgender SNP members and supporters and is due to stage its inaugural conference in Glasgow today with Nicola Sturgeon as the keynote speaker.
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