David Steel: First big test will see Salmond a statesman or spoiler

AN OUTRIGHT victory in a Scottish Parliament election was never envisaged by those who supported a proportional electoral system for Holyrood. The Additional Member System sought to bring the number of votes cast into close alignment with the number of seats won, and make power-sharing a defining feature of devolved government. As it turns out the SNP's 45 per cent of the popular vote was enough to give them more than half the seats and overturn many of the assumptions and expectations of Scotland's political establishment. It is now the Nationalists' responsibility to use that majority wisely. Their first big test is their attitude to the Scotland Bill currently making its way through the legislative process. The bill - whose principles were endorsed by the last Scottish Parliament - will soon leave the House of Commons, and go the House of Lords and the new Scottish Parliament for their approval. It is in the interests of Scotland to see that bill become law.

This Scotland Bill proposes the most significant shift of financial powers back to Scotland since 1707. It devolves powers over income tax, public borrowing and a plethora of others areas proposed by the Calman Commission. As a Liberal Democrat, I wholly support its aim to strengthen the powers of the Scottish Parliament and to make it more accountable to the Scottish people.

The Steel Commission, which I chaired, outlined our vision for further devolution within a federal UK. It did not seek to prescribe the final settlement and we advocated a second Constitutional Convention to seek consensus among political parties and beyond on the future shape of Scottish devolution. As part of that it also envisaged a significant reassessment of the needs based funding formula to replace the Barnett formula.

The Calman Commission became the equivalent of that second convention and its recommendations, which borrow heavily from our proposals, were endorsed by the Conservatives and Labour as well as our own party. I have no doubt that individual party preferences - including ideas considered by the Steel Commission - will be raised in debate as the bill continues its legislative process, and Liberal Democrats and others will certainly respond to those points. But the strength of the Scotland Bill - its legitimacy - lies in the cross-party consensus, reinforced at the UK general election, that is right for constitutional change.

Of course, consensus building is not something that the SNP does well. Of Scotland's four main political parties, the SNP is the only one that refused to participate in either the Scottish Constitutional Convention or the Calman Commission, despite the clear intention of both to devolve power. The First Minister is working hard to portray himself as a reasonable man with a cooperative approach. This is not something for which he has been famed in the past. But Alex Salmond will be judged by deeds, not words - and his unexpected Holyrood majority will flush him out. He no longer needs to do deals with others to pass laws, get budgets through - or determine the wording of a Scotland Bill legislative consent motion. So now that he doesn't have to, the question is: will he? Will he work with others to ensure that the bill is acceptable to both parliaments, or will he play a spoiler for narrow ends?But for a bill to become an Act requires more than consensus - it requires government support too. The last Labour government produced a White Paper but no bill. The Coalition has gone the extra mile but it is worth noting that of its two parties, the Conservatives promised in their 2010 manifesto another White Paper only. The Liberal Democrats promised a bill, and that is what Michael Moore, the Scottish Secretary, has delivered. I know Michael well. He is cooperative by nature and has a firm grasp of detail. These attributes have helped him to steer the Scotland Bill skilfully through the Commons thus far, holding together cross-party support. The Scottish Parliament's vote in favour of the Bill - with SNP support - is also an endorsement of his approach.

But that SNP majority at Holyrood does change the picture. Alex Salmond has made clear that he wants an indication from the UK government that it will make further provisions in a number of areas including borrowing powers, corporation tax and the Crown Estate, and argues that he has the mandate to demand them. Given that these matters are, by definition, reserved to Westminster, and the Holyrood election provided a mandate for devolved issues, that interpretation is certainly open to challenge. But, in politics, other things count and the SNP's Holyrood majority means that it could, at the risk of losing all the new powers, vote against the Scotland Bill when it comes back to the Scottish Parliament in the late autumn.

That eventuality can and should be avoided. Last Thursday's long meeting between the First Minister and the Secretary of State shows a welcome willingness on both sides to engage. As it stands, Mr Salmond has said that he will provide the UK government with further thinking on the changes he seeks. The onus is now on him to make a detailed and convincing case. He needs to show that his plans would not just strengthen the bill, but will not jeopordise its passage either.

After all, it is not enough for any changes to please the Scottish Government - or indeed the Scottish Government and the Coalition. This bill has to get through the House of Lords too, and that means keeping Labour, Conservatives and others on board. The peers too, will have changes that they wish to make. I have said previously that it is right and proper that they exercise their right to scrutinise the bill and seek to improve it. Like the Scottish Government, their case will rest on its merits and their capacity to build on consensus rather than break it.

The press will anticipate with relish a stand-off between Westminster and Holyrood. That would make good copy, but it would serve the Scottish people poorly. They want to see a mature and effective Scottish Parliament that is empowered to act on their behalf and which is answerable to them for the decisions it takes and the money its spends. It is not in their interests for anyone to sabotage the Scotland Bill or claim victory in a fight over its content. Those games will only breed cynicism and put at risk a piece of legislation that has generated considerable support but which the opponents of devolution would still like to kill off. Consensus has brought us this far, and consensus will take us further still.

• Lord Steel of Aikwood is a Liberal Democrat peer and a former Presiding Officer of the Scottish Parliament