In Scotland, success in politics depends on being a Scottish nationalist. This does not mean that you have to be a member of the SNP, but what's best for Scotland must be at the centre of your politics. It is perfectly possible to conclude, as most political parties in Scotland (and probably most Scots) do, that Scotland's interests are best served by being part of the Union. But that conclusion must be based on a calculation of what is best for Scotland.

The SNP has had its disasters in government but that bigger picture of putting Scots first has been the recurring theme of its government, with policy moves such as abolishing prescription charges conveying the sense that it is in control and able to deliver.

Iain Gray - regarded by all who work with him as competent and decent - and the Scottish Labour Party forgot that truth in their campaign for the elections of 5 May. They campaigned initially on the basis that Scotland should lead the fightback against the coalition at Westminster.

The unpersuasiveness of the argument that Scots should vote Labour in the Scottish Parliament elections to assist Labour's position in the UK parliament underlined the inbuilt advantage that the SNP has in all Scottish elections: namely that it is a nationalist party, calculating its positions on domestic issues exclusively by reference to the Scottish interest.

A knotty problem

After making that mistake, Labour could not get back into the game. The SNP's strategic position was that it was fighting for Scottish interests, while Labour was struggling to find a place for itself in UK politics. Labour's attempts to change this impression inevitably failed, because the SNP is led by a person who can most easily command the Scottish media, who is extensively funded by Scottish business and, above all, who has a record of what appears to be persistent competence and putting the Scots first in domestic affairs.

Labour is a UK party. The SNP is a Scottish party. That difference is now a structural problem for Labour in Scottish politics.

To combat it, Scottish Labour needs to convince the Scottish public that its concerns are Scottish, too. A good starting point would be a leader who can show the Scottish people that he is independent of the Westminster leadership and can deliver for the country. Let's hope that Jim Murphy's "root-and-branch" review, ordered by Ed Miliband, will consider this.

Meanwhile, across the UK, this simple message of delivering for the people rather than the politicians appears to have passed the Liberal Democrats by. Even their demand for a referendum on the Alternative Vote as a condition of joining the coalition government suggested that the Liberal Democrats were concerned most of all about themselves.

As if to underline this idea that they are a "set of men who have interests aside from the interests of the people" (to quote Abraham Lincoln on politicians in general), they demanded that their referendum - and everyone understood that it was the Liberal Democrats' referendum - should take place on the same day as the local, Welsh and Scottish elections.

Voters have shown little interest in electoral reform. Most saw it simply as a device to help the Liberal Democrats. Many are disappointed that the party used its first taste of power to put its own interests first - something that exposed the Lib Dems' disconnection from the concerns of ordinary voters.

Nick Clegg's early success as Liberal Democrat leader was in appearing to articulate and share the concerns of the general public, as opposed to the political class. Yet the tuition fees debacle, followed by the AV referendum, redefined him as an unreliable politician whose concerns were not those of the country.

The Liberal Democrats' failure helped Labour throughout England and Wales on 5 May. We won 800 council seats. The Lib Dems lost around 700 seats. But their failure did not help Labour pick up Tory seats. The Tories held on, or made advances, because they, too, were picking up some Liberal Democrat votes.

Challenge ahead

Ed Miliband is doing a good job in addressing the detail of policy and seeking to define a strategic position that would give us a much wider appeal than we now have. Building that will take time; it is, after all, only a year since we lost the general election. But once one party gets a reputation for understanding the public's concerns and being able to respond to them, it quickly squeezes the life out of the other main party. This is what the SNP has been doing to us in Scotland over the past four years and it is what we did to the Tories after 1992. You don't have to be in government to do it.

Neither the Tories nor Labour are there yet. The aim is to be the party that best understands people's preoccupations and concerns and is most effective at addressing them. The judgement that voters make in an election is very often a different one from the short-term frustration reflected to a pollster.

Labour's challenge is to convince the public that our progressive values and our current priorities reflect its concerns. The 5 May election indicates that we have some way to go. And we have much to fear from a resurgent Conservative Party and an emboldened SNP.

Labour faces a real challenge. In order to regain power in Scotland and to ensure Scotland does not break away from the UK, which I think is unlikely, Scottish Labour must demonstrate that it puts Scotland first. At the same time, Labour, including Scottish Labour, must convince the people of the UK that it is putting the people of the UK first. It is a challenge unique to Labour. The Tories can win in Westminster without Scotland. Labour can't.

Charles Falconer is a Labour peer and the former justice secretary