Labour leader Johann Lamont has promised to deliver "the maximum ­devolution Scotland would want" under plans to be unveiled tomorrow.

Labour's devolution commission will publish its proposals to transfer more powers to Holyrood ahead of the party conference in Perth next weekend.

The package will include handing MSPs greater control over income tax.

Yesterday, Ms Lamont said: "Many people had been calling for us to bring forward a concept called devo max. We believe this is the maximum devolution Scotland would want before the Union itself starts to get picked apart and Scotland loses out.

"We have tried and tested our ideas to the final degree so we can propose a settlement for Scotland that makes sense. I believe it can herald a new chapter in Scottish politics."

The tax plans will form part of Labour's manifesto for the 2015 Westminster election if approved by delegates on Friday. The package of tax powers on offer would make MSPs responsible for raising about 40% of the money they spend.

Last week, former prime minister Gordon Brown urged the party to give Holyrood full control over the top rate of income tax, enabling MSPs to make the regime "fairer".

In a separate development, the STUC will today publish proposals to give Holyrood control over two-thirds of the money it spends.

The unions will call for all of income tax to be devolved and funds from other taxes raised in Scotland, including VAT, to be "assigned" to the parliament rather than going to the UK Treasury.

Powers over welfare and employment rights should also be transferred to Holyrood, the STUC reports says.