Willie Rennie, the articulate Scottish Liberal Democrat leader, has been warning the SNP not to place too much emphasis on the issue of national identity, especially in the context of next year's referendum.

It's strange that a party that is honestly and straightforwardly a national party should be given such advice. Right now, with UK LibDems meeting in Glasgow, it is pertinent to ask about the "identity" of the LibDems themselves.

The most prominent Scot in the party is Danny Alexander. As Chief Secretary to the Treasury he is the fourth most important person in the UK Government. Mr Alexander has been an effective and industrious assistant to the Chancellor, George Osborne. He has implemented Mr Osborne's austerity polices with zeal. I am not necessarily complaining about that; it is what the Coalition set out to do, and it undoubtedly inherited a grotesque financial mess.

But I am not sure the LibDems were actually elected to pursue these policies with such apparent zest. They were certainly not elected to put up student tuition fees, for example. In implementing the policies of the senior partners in the Government, the LibDems are confusing many of us, particularly in Scotland, as to what exactly their party works for in government, what it stands for, and where it is going. I have never had a similar problem with the SNP.

Not long after our Scottish constitutional referendum, which Mr Rennie insists should not be about national identity, the LibDems will have to decide what they are going to tell people in the build-up to the 2015 General Election. Are they prepared to form a coalition government with Labour? If so, will that ensure the dismantling of many of the policies they have been pursuing and activating for five years?

This is the sort of question that raises the question of UK "identity". What sort of country is the UK supposed to be, and what do the LibDems want it to be? If the LibDems themselves do not have a clear identity, and do not know what they stand for, what will be the point of voting for them?

Meanwhile, the problem with the LibDems in Scotland is they are not sure how Scottish they should be, A few years ago I reviewed, for this newspaper, Sir Menzies Campbell's excellent autobiography. Reading the book, I was struck by a sense of dual identity. A respected "elder statesman" in the party, he seemed to be very Scottish indeed when it came to the Scottish legal system, in which, for much of his career, he excelled. He identified with it and cherished it.

But he seemed less sure of this Scottish identity when it came to politics. He certainly did not want to be typecast as "tartan". In the Scottish context, he could not see any LibDems-SNP coalition working. He did indicate his party would be prepared to negotiate with the SNP, but only if the Nationalists dropped their commitment to a referendum on independence.

What I read into these comments is that the LibDem 'identity" is probably very Unionist, indeed so Unionist the LibDems would be prepared to work with either of the big UK parties, the Tories or Labour, even though both the policies and the philosophies of these two parties are so very different. Senior LibDems' strategists might argue that by joining either of these parties in UK government they would be able to temper any ideological excesses. At that point I would return to the record of Mr Alexander in office.

It is possible that if the LibDems had a more clear-cut identity they could finally emerge as a credible "third party" in British politics. Right now, the role of UK third party is, disastrously, being enthusiastically chased by UKIP.

What I would really like to hear from the LibDems is more about their vision of the UK and, indeed, its future identity. Right now what seems to be the point of the party is to prop up the Tories - and in time, possibly Labour - in coalition. Not much identity there.