Reality television, as George Galloway will tell you, is a fabulous way for a politician to raise his public profile. Still, one imagines Jim Murphy could have thought of better ways to make his mark on the national consciousness than being outed as a former Communist by Tommy Sheridan on Big Brother, three months into his service as Scottish secretary. Murphy shows no sign of embarrassment when pressed on Sheridan's revelation in January of his youthful flirtation with the Revolutionary Communist Party. “It’s more than half my lifetime ago,” he says, sitting back with his feet up in his Melville Street office. “I went to a couple of meetings, thought ‘Nah, this isn’t my type of politics,’ and joined the Labour party.” Whatever the truth of allegations that he was once banned from a Labour students conference for being too left-wing, Murphy’s political energies these days appear firmly focused on the job in hand.

Shortly after accepting the Scotland portfolio, Murphy raised sceptical eyebrows with his insistence that his role was not “a party political one” – an assertion that looks to have been undermined by his frequent public disagreements with Alex Salmond’s SNP government. “I’d like a position where, on a day-to-day basis, we could try to find more common cause,” says Murphy. “But the SNP seem to be committed to a policy of no compromise with economics. They’ve been robbed of an economic logic by their own words. The first speech Alex made as first minister was the arc of prosperity – Iceland, Ireland… He just overstretched himself; a wee bit too arrogant, a wee bit too cocky.”

Still, there’s no hiding his underlying affection for the gregarious first minister, whom he recently slammed for being more interested in Westminster than in Scotland. “Do you play football?” asks Murphy, the captain of the parliamentary team. “Play the ball rather than the man, that’s what I want to do. I don’t criticise him personally. He loves Scotland as much as I do – but it’s different political philosophies. I don’t doubt his patriotism; I doubt his judgment.”

Murphy implicitly alludes to a prime Achilles heel of his unionist cause: with his endless avowal of Scotland’s ability to prosper alone, Salmond can appear to have stuck a nationalist flag in patriotism itself, leaving unionists sounding downbeat by comparison. “It’s a harder argument to make,” concedes Murphy, “which is that I love my country so much that I know it’s stronger in the UK. I want Scotland to be a big player on the world stage. I want us to have an influence at the United Nations, the European Union, the World Trade Organisation. And that means being an equal part of the United Kingdom.”

This emphasis on the United Kingdom—in particular, on the abstract concept of “Britishness”—has been one of the hallmarks of Gordon Brown’s government, with critics sniping that it’s a simple ruse to deflect English mistrust of the prime minister’s Scottish roots. But Brown’s semi-jingoistic rhetoric came back to haunt him at the recent wildcat strikes in protest against the use of foreign workers, where demonstrators were seen brandishing placards reading, “British jobs for British workers” – a phrase coined by Brown himself at the 2007 Labour conference. Has the government’s obsession with Britishness served to fuel xenophobia?

Murphy looks uncomfortable. “I don’t think so,” he says, “but then everyone has their own view. I mean you’ll have your view, but I mean my view is probably not…” He takes a deep breath. “I don’t know who’s against British jobs for British workers. You want British workers to get jobs.”

It can be taken to imply no British jobs for non-British workers, I reply. “Yeah, okay,” says Murphy, engrossed in thought. “I guess the way I would argue it would be: British workers for British jobs. We’re not training enough people for a low-carbon economy; there aren’t enough people coming out of the factories and into green-collar jobs. So if we don’t get our act together—you can have all the technology and all the political will—but unless you get British workers for British jobs in things like this, we’re going to get left behind.”

As unemployment rises, politicians will likely come under more fire than ever for being out of touch – but Murphy should escape relatively lightly, after his tough early life. “I had a proud, good, but poor upbringing in a housing scheme in Glasgow,” he says, “where four generations of my family lived in the same two-bedroom flat. Then we emigrated to South Africa, and I saw a very different kind of poverty, in the vile racism of South Africa during apartheid. Kind of gives you a wee sense of right and wrong, a decent grounding.” That stood Murphy in good stead as his political career got underway after his return to Britain: elected to parliament in 1997 after a spell as NUS president, he moved swiftly up the Labour ranks, attracting notice as minister for Europe during the wrangling over the Lisbon Treaty.

His promotion to Scottish secretary last October marked Murphy’s entry to the top tier of government – but many consider the role to have been emasculated after the transfer of many of its responsibilities to the Scottish executive in 1999. Is the job still as important as it was when Donald Dewar held it?

“I think it is,” says Murphy, “particularly at this time. Scotland needs a full-time voice around the cabinet table, and at the National Economic Council. It would be peculiar if it didn’t.” But it didn’t, I point out, for more than a year before Murphy’s appointment, while Des Browne juggled the job with his responsibilities as defence secretary. Was that a mistake?

“Yes,” says Murphy bluntly. “He did it well. He did two jobs as well as any human being could do. But it wasn’t doable. I think it was wrong, it was a mistake, and we’re back to where it should be.” This unusually candid admission of an error of judgment on the prime minister’s part comes at a time when many are questioning his fitness to lead the country; one rumour has it that Brown may be considering taking up a job as a global financial regulator. Does Murphy think he’d be well qualified for that line of work?

“No, because he’s got a job.” Murphy fixes me with an unblinking stare as a clock ticks noisily by his side. “Gordon Brown is a leader. I’m not being critical of anybody else, but which other world leader is as economically literate as Gordon Brown? Angela Merkel, Nicolas Sarkozy…hopefully Obama gets there—Obama’s a phenomenal, an amazing individual—but he doesn’t yet have the economic experience of Gordon Brown. There just isn’t another world leader with that economic wherewithal.”

This argument seems to have been all but lost on the British public, whose estimation of the prime minister seems to be falling in all but direct correlation with the nation’s economic fortunes. Murphy is a pillar of empathy. “People are rightly angry, anxious and frightened,” he says. “Because no-one’s lived through this before, there’s a great uncertainty. And understandably that affects the public’s mood. We’re the government, and it would be implausible to suggest a governing party could buck that trend.

“And politics gets harder the longer you’re in power. The Labour party has never been in power for two full terms in its history – and now we’re trying to get a fourth! In 1987 we’d have pinched ourselves at the idea of doing one.” During Murphy’s eleven years in parliament, his party’s most sustained period of electoral success has coincided with a rapid, constant upward trajectory in his personal career. If the polls are any guide, both are set for a tumble come next summer’s likely general election – but Murphy seems more than tough enough to take it.