A CROSS-PARTY group of MSPs has slammed draft legislation that would devolve more power to Holyrood, saying current proposals fall short of what was agreed by the Smith Commission in the aftermath of the independence referendum.

The Devolution (Further Powers) Committee, which has members of all five parties represented at the Scottish Parliament in its ranks including the SNP's Linda Fabiani and Lib Dem Tavish Scott who sat on the Smith Commission, said draft clauses published by the last UK Government fell short in a number of key areas compared to what had been agreed.

David Cameron had pledged that the recommendations of the Smith Commission would be implemented in full, however, the committee found that much of the proposed legislation was lacking "both in spirit and substance".

The group, which has taken evidence from a series of experts, raised concern over a lack of clarity in the draft clauses and called on the new Scottish Secretary David Mundell to address the concerns that powers had been watered down.

The committee found that there was no provision in the draft clauses for creating new welfare benefits, that there were "significant issues" with the devolution of income tax which could lead to individuals being taxed twice and raised concern over proposals to cement the permanence of the Scottish Parliament and devolution of the Crown Estate.

The group's convenor, Bruce Crawford, said: "In short, if the Smith Commission recommendations are a baseline or a minimum, we are not there yet as far as the clauses are concerned. The Committee is disappointed that the currently proposed legislation sells Smith short."

The report backed up a concern raised by the SNP in the wake of the publication of the draft clauses, when the party claimed that a requirement to consult the Secretary of State over changes to universal credit effectively handed the UK Government a veto over changes. The report concluded that the clauses in question "could be considered or perceived as a veto", despite the previous administration at Westminster denying it would be the case.

MSPs also criticised a lack of clarity in several key areas, and backed up concerns over competition and confusion that may arise from the creation of 'two Crown Estates'.

Mr Scott, whose LibDem colleague Alastair Carmichael was Scottish Secretary when the draft clauses was published, said: "I know what Smith wanted to do. I know what we negotiated... I have no difficulty whatsoever in demanding that the full intent of what we agreed on a cross-party basis is implemented by the UK Government."

The report called for a triple lock over the permanence of Holyrood, recommending that a referendum should be held if the Scottish Parliament's future was ever called in to question, while both the UK and Scottish Parliaments would have to vote for its abolition.

In terms of income tax, it found significant issues still to be resolved in terms of how a Scottish taxpayer is defined, how taxes will be collected and a need to avoid double taxation.

Speaking about welfare clauses, Ms Fabiani said: "My real concern is that if the draft clauses were implemented as is, it would cause confusion and potentially hardship for those who require assistance through welfare."

A spokesman for Nicola Sturgeon backed up comments made by her deputy John Swinney, saying that the committee report supported the Scottish Government's claim that the draft clauses would not deliver what was recommended by Smith.

Mr Swinney said: "I welcome this all party report which endorses our long held view that the draft clauses published by the UK Government before the election simply fail to reflect the Smith Commission recommendations.

"I share the Committee's concern that in a number of key areas, particularly in relation to welfare, the draft clauses do not meet the spirit or substance of Smith. I expect the UK Government to take the unanimous views of the Devolution Committee very seriously and amend the Scotland Bill before it is introduced.

A Scotland Office spokesman said: "The UK Government is committed to delivering more devolved powers through the package outlined by the cross-party Smith Commission. We will work to bring forward a Scotland Bill on this basis and ensure the Scottish Parliament becomes one of the most powerful devolved parliaments in the world. The Secretary of State has been clear there will be a full parliamentary discussion of these issues where differing views can be heard."