ELECTING a sizeable bloc of SNP MPs in May's general election would put pressure on the next UK government to deliver extra powers for Holyrood, the party's deputy leader has insisted.

Stewart Hosie attacked as inadequate the package of powers agreed by all the Holyrood parties - including the SNP - during the Smith Commission process last year.

But he conceded there was "much to welcome" from the deal and called for the swift transfer of a number of powers, including control over Air Passenger Duty, a tax on flights, and the Work Programme, the Department for Work and Pensions' employability scheme.

Dundee MP Mr Hosie, who became SNP deputy leader in November, said: "It's clear that the Smith Commission didn't go far enough - leaving far too many powers over the economy and welfare in the hands of the Westminster establishment, which is likely to disappoint many people who voted No as well as those who voted Yes.

"Under the proposals the Westminster Government will still control around 70 per cent of tax raising powers and around 85 per cent of welfare powers. That isn't Home Rule.

"But there was much to welcome in the agreement and Westminster must guarantee at least the delivery of the

powers outlined in the Smith Commission's report."

He added: "While some of the new powers agreed will require legislation - many of them can be transferred right now if Westminster has the political will.

"Westminster must now resolve to ensure that the New Year means new powers for Scotland.

"And a strong team of SNP MPs elected in May will mean we can hold the Westminster parties to account on their promises and deliver the powers we need to make Scotland a fairer, more prosperous place for everyone who lives here."

The SNP believes the issue of further devolution will dominate the general election campaign.

The Nationalists claim the Smith Commission package - which will give Holyrood almost full control over income tax and considerable responsibility for welfare - will only be delivered in full if a large number of SNP MPs are elected, despite pledges from the main UK parties.

Scottish Labour leader Jim Murphy repeated his party's election pitch to voters in his New Year message when he warned a vote for the SNP could hand David Cameron the keys to 10 Downing Street.