The former prime minister said Labour was breaking with the “weaker” plans of the Tories and Liberal Democrats on the issue.
Mr Brown said “further radical change” was needed to ensure the package of new powers coming to Holyrood was “delivered” in a “fairer” way as he and Scottish Labour leader Jim Murphy unveiled plans to devolve key welfare benefits.
The former prime minister is widely seen as one of the architects of the Smith Commission process set up to deliver “the vow” to give Scotland more powers made by the main unionist parties in the run-up to last year’s independence referendum.
However, the former prime minister yesterday shattered the consensus among the unionists parties over the Smith agreement, which backed the devolution of a range of benefits to support older people, carers and disabled people.
Mr Brown suggested the UK government had watered down the intentions of the Smith Commission with plans that were too restrictive, as he delivered his first major policy speech since the referendum.
He accused the coalition government of taking a “narrow” approach to devolving powers to Scotland and of wanting to retain the final say over issues such as welfare and the so-called “bedroom tax”, which reduced the income of claimants living in under-occupied homes.
Mr Brown, speaking in Edinburgh, said Scottish Labour would campaign on a plan to allow Holyrood to top up and vary the UK’s state pension, unemployment and child benefit, as well as the full devolution of housing benefit – a package he branded as “the vow plus”.
He said: “For having studied the coalition’s statements and their draft laws, we can now show how we will implement the vow in a fairer and more radical way that advances social justice in Scotland.
“And so we are breaking with the Conservatives and Liberal Democrats whose weaker version does not go far enough and we are putting forward the stronger version. It is in fact the vow plus further radical change.”
Mr Murphy said the plan to devolve welfare benefits would “shatter” the “chain of disadvantage” of poverty in Scotland and allow Holyrood to compensate for any cuts made to welfare by making up the shortfall.
Mr Brown, who is stepping down as an MP after 32 years at Westminster, told Labour supporters that a failure to devolve the powers over benefits would leave Scotland at risk of polices such as the bedroom tax and cuts made by the UK government.
He added: “Jim and I have examined the coalition’s draft laws and we believe that the welfare powers need revised. We would hope for all party agreement and favour co-operation.”
Scottish Conservative leader Ruth Davidson, said Mr Brown was “yanking the Labour party back to the bad old days of high tax”, while Scottish Liberal Democrat leader Willie Rennie said the party was “making it up as they go along” on devolution.
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