“If the SNP lose the election in Scotland, the debate on independence stops”, declared Tommy Sheppard, a promoter of stand-up comedians before becoming an MP. Surely this was his most acclaimed one-liner ever.

Across a vast swathe of opinion, the prospect of “the debate on independence stopping” raised the spirits of the nation. An extra incentive was instantly created to dispense with Tommy and his motley band. Could relief really be achieved so easily?

Alas, the sound of silence is not entirely within Tommy’s gift. The background drone will continue and doubtless rise again in more propitious circumstances. But even a temporary respite would be welcome in deference to pressing matters.

Read more: Wind energy: How is our ‘second industrial revolution’ coming along?

The SNP has two obvious difficulties as a General Election approaches. Well, probably a lot more than two but let’s not be greedy. First, it is trying to sell itself as an agent of change when the reality is it can only act as an obstacle to change.

If people want change, they need to vote for it. Furthermore, if they want Scotland to be part of that change and to maximise benefit from it, the sensible course is to return MPs who are part of government rather than in opposition - which means, wherever the serious option arises, voting Labour.

The problem for Humza Yousaf was illustrated by his speech on Monday when he told us we could all be £10,200 a year better off with independence. I love the precision. Is the two hundred quid meant to swing it? Or does ten grand just sound a bit plucked out of thin air?

Anyway, nobody took it seriously because, even overlooking the other chasms in his argument, it is a long-term possibility which people will not be voting for in a General Election. The offer remains as illusory as it is improbable. Meanwhile, the SNP at Holyrood is cutting everything and raising taxes.

That, however, leads to the SNP's second problem. If it cannot plausibly invite people to vote for independence and its £10,200 bonus then what else does have to offer in the interregnum? That is the trap it has set for itself by being such a one-trick constitutional pony.

The Herald: Mhairi Black has been embroiled in a row with Joanna CherryMhairi Black has been embroiled in a row with Joanna Cherry (Image: PA)

Not even their best friends could plead with Scottish voters to return the current 44 jokers to Westminster on grounds of calibre or influence. There are honourable exceptions who make productive use of their presence there but most would be better at home for all the difference they make to anything.

Indeed, while heading for the Westminster exit, Mhairi Black, pride of Paisley, accused her colleagues of becoming “slightly more comfortable than they should be” in Westminster, which is the polite way of saying they love it there and are not overburdened with work, other than to shout abuse at the Tories once a week.

Understandably, Joanna Cherry KC, MP, took exception to Ms Black’s analysis. “It’s not easy being an opposition Member of Parliament at Westminster, but if you work hard and if you’re present there, and if you build alliances, then you can achieve successes,” she said and that is absolutely true.

By the same token, however, any serious politician would prefer to be in government as I’m sure Ms Cherry would agree. And that is something even diligent SNP MPs cannot offer, just as Labour couldn’t in the Miliband-Corbyn years. This time it can, and therein lies a big difference.

The other interim selling point for the SNP, while independence is not in vogue, could have been its competence as the devolved government of Scotland, with 16 years to get that right. It would be fair to say it is now further away than ever from projecting that image.

Take two current case studies to demonstrate why it is as counter-productive as a government in Scotland as it is as an opposition at Westminster. The first involves the curious case of the Bully dogs which have become a symbol of the SNP’s core belief that doing things differently must always take priority.

There is nothing inherently political about measures to safeguard the public from these animals. The UK Government did so in response to alarming episodes and invited the Scottish Government to join in. It declined, presumably on grounds that Michael Gove was not going to tell us what to do with our Bully dogs.

As a result of this episode, I have learned we have a Community Safety Minister named Siobhann Brown, to whom it had apparently not occurred that Scotland would become the safe haven for Bully dogs once they were banned in England. She now describes this as an "unintended consequence of the UK Government’s policy”.

No it isn’t. It is the entirely predictable consequence of the Scottish Government’s policy not to do sensible things on a cross-border basis. I think most people are tired of this brand of devolved government based on determination to drive difference and grievance at every opportunity.

Read more: SNP budget moans show need for a full review of how our money is spent

My second example is the Post Office Horizon scandal. Here there actually was an opportunity to do things differently and better, not as a point of principle but because, for reasons that long pre-date devolution, different legal systems apply, with decisions to prosecute in the hands of the Crown Office and procurators-fiscal rather than the Post Office.

It could have been a source of pride if our independent prosecution service or Justice Minister spotted something amiss. Instead, pathetically, we ended up even further behind than the rest of the UK in quashing convictions while the Crown Office admitted it was “very much closer to the start of its journey” in addressing miscarriages of justice.

Is it just possible that a Scottish government which accepted that “the debate on independence stops” at least temporarily might be better at doing what is within its powers? Meanwhile, competence in government would be the last reason for anyone to vote SNP in the hope of change.

So let’s take Tommy Sheppard at his word:  vote for change and stop talking about independence. Two for the price of one.

Brian Wilson is a former Labour Party MP and Energy Minister