The new millennium was accompanied by a burst of optimism and a sense that the world could be made a better, fairer place.

Much of the impetus for that push against poverty and inequality came from the UK Make Poverty History campaign, which was particularly well-supported by Scottish churches and civic groups. The campaign crystalised into the Millennium Goals agreed by the G8 nations at the Gleneagles Summit in Perthshire in 2005. At the same time the UK Government was pledging to eclipse child poverty. But the global financial crisis three years later was used by governments everywhere to sideline anti-poverty measures.

For a time there seemed to be a general acceptance that there was no alternative to belt-tightening but the consensus around austerity is rapidly unravelling right across Europe on the back of increasing evidence that we are not "all in it together" after all. That is why the intervention in the debate yesterday by Britain's most senior Roman Catholic, Cardinal Keith O'Brien, was a timely one.

The pretext for the cardinal's statement was to back the call by the Scottish Catholic International Aid Fund for a Robin Hood tax on financial transactions, to fund anti-poverty measures at home and abroad and help developing countries tackle climate change. This idea is not new. The Church of Scotland publicly backs the same campaign and the Archbishop of Canterbury voiced his support during the St Paul's protest last year.

It is the timing of the cardinal's contribution and his pointed criticism of the moral dimension of the Coalition Government's policy that are significant. "It is not moral just to ignore [those trying to make ends meet] and to say 'struggle along', while the rich can go sailing along in their own sweet way," he said. By coincidence new figures published yesterday show the UK's 1000 wealthiest people have become even richer since last year. On Friday Barclays revealed reward packages for its employees triple the size of the dividend to shareholders. Meanwhile, record numbers of Scots are relying on food banks and, as The Herald reports today, 40% of Scots with learning difficulties will be worse off after the introduction of new disability benefits. Charities contradict Government assurances that the reforms will not disadvantage those with genuine disabilities. At the same time, the Government is considering changing the definition of child poverty after its own figures reveal huge rises in their numbers.

Added to a budget that found new ways to squeeze pensioners and those on low incomes while handing a tax cut to the richest, the impression is of government by the rich for the rich. That is why the cardinal's words strike such a strong chord.

A Robin Hood tax on stocks, bonds, foreign currency and derivatives, even set at a minuscule 0.05%, could raise £250 billion a year to help the poor. Polling by Oxfam shows 62% support in Scotland. The UK Government argues that unilateral action would cost investment and jobs, though some experts deny this. Global action is certainly desirable but the US would find it harder to resist the idea if Europe adopted it. And yet the UK Government is one of the main opponents of an EU-wide transaction tax. Recently the Welsh First Minister voiced support for the tax. Alex Salmond could usefully add his backing to that of Carwyn Jones and Cardinal O'Brien. A Robin Hood tax is an idea whose time has come.