IT wasn't her intention, but Nicola Sturgeon made an eloquent case for unionism when launching the SNP general election manifesto in Edinburgh yesterday.

She pledged the commitment of her party's MPs at Westminster to a united struggle with left and progressive allies against austerity and British nuclear weapons.

Across Britain, the SNP also seeks higher minimum wages and an income tax increase for the rich.

True, Ms Sturgeon wants such unity to last only so long as the union and not a moment longer. But her current stance exposes some contradictions in the SNP case for separation from England and Wales.

For a start, by placing such issues above any immediate call for Scottish independence, she acknowledges the real underlying priorities of the majority of Scots, whichever way they voted in last September's referendum.

Those priorities are for jobs, public services, a living income, decent housing, fair opportunities for themselves and their children, security and peace.

A significant number of Labour supporters voted Yes to independence last year because they believed those aspirations would more likely be met in an independent Scotland, not because they are nationalists or more patriotically Scottish than many No voters. 

If they believed a Westminster parliament and government would enact policies to those ends, the appeal of independence would fade.

And yet here is the SNP, seemingly pledging its MPs to help fight for such a parliament and government.

Perhaps they do so from cynical calculation, believing that a Labour-led government will fail to carry through a progressive, anti-austerity and anti-war programme.

The SNP could then contrast its own policies to those of Eds Miliband and Balls, mop up even more of the Labour vote in Scotland and win a second referendum for separation.

However, the somewhat thin SNP manifesto unveiled yesterday was hardly red in tooth and claw.

Its minimum wage target by 2020 of £8.70 an hour is higher than Labour's by pennies rather than pounds.

While promising to increase current and capital expenditure in Scotland, the enthusiastically pro-business SNP programme places extraordinary faith in the private sector to deliver, once bribed with sufficient public subsidies and incentives.

In fact, Stronger for Scotland proposes no extension of public ownership whatsoever into any industries or services. Monopoly ownership of energy and public transport is to be left untouched. By this measure, the Welsh Labour government is a reincarnation of Lenin and the Bolsheviks.

Of course, it has been heartening to hear the SNP, Plaid Cymru and Green Party leaders putting the case for abolishing Trident and against any new generation of nuclear weapons in Britain.

They have shattered the efforts of the Tory, Lib Dem and Labour parties and the mass media to muzzle public debate on the issue.

Nonetheless, the SNP still proclaims its new-found fidelity to Nato, the aggressive US-led atomic alliance which has expanded across Europe and the Asian subcontinent to threaten Russia and China.

More than 50 Labour parliamentary candidates have committed themselves to vote against any post-Trident nuclear weapons system.

We need a united struggle against weapons of mass murder, inside Britain's parliaments and outside, until they are abolished in every one of our three nations.

Like Labour, the SNP also eulogises the anti-democratic, pro-austerity, pro-big business European Union.

Workers in a nominally "independent" Scotland would still be ruled by EU Commission and European Central Bank diktat, when what we need is a united struggle across Britain against EU membership altogether.