Are hedge fund managers the Tories' trade unionists?

BBC business editor Robert Peston on Central Office donations

Labour leaders and Labour prime ministers have since time immemorial (well almost) taken millions of pounds of funding on behalf of their party from trade unions, and devoted a considerable slug of their waking hours to telling the world that these trade unions are not bossing Labour policies.

Tony Blair, as prime minister, made it something of a personal speciality to take trade union money with one hand and to sock trade union leaders in the moosh with his other. But that never stopped the Tory Party accusing him and his successors of being in hock to the brothers.

So it probably won't be especially easy for David Cameron to bat away as irrelevant the statistics published today by the independent Bureau of Investigative Journalism of the extent to which Conservative Party Central Office has become dependent on cash donations from companies and individuals working in financial services.

The trends are striking: in 2005, the financial services industry contributed 25% of Central Office cash donations; that had risen to 52% in 2009 before falling back to 51%.

It is probably worth overlaying on to the funding statistics separate research on the number of Tory MPs who have worked in the City and financial services. According to an analysis by the Mirror in January, 134 of 498 Tory MPs and peers were or are employed in the financial sector - which includes 70 MPs.

The question, which of course arises, is whether this gives the Tory Party and Tory Members of Parliament a deep and useful insight into one of the UK's most important industries. Or whether it biases the Conservative members of the government to favour this industry in a way that is unhealthy for the country as a whole.

If you were going to give the Tories the benefit of the doubt, you would refer to the performance of the former Barclays banker Andrea Leadsom as a Conservative member of the Treasury Select Committee. When the committee grilled Barclays' chief executive Bob Diamond last month, Andrea Leadsom was one of his more acute and merciless interrogators.

Those however who wish to see conspiracies will point out that for all ministers' tough talk about curbing bankers' bonuses, what will emerge as and when Project Merlin is formally announced is promise of restraint but the reality of millions of pounds being awarded to thousands of top bankers.

It should be pointed out, however, that the simplest conspiracies won't fly: the bulk of funding for the Tory party doesn't come from bankers; arguably the most important group of Tory donors are hedge fund managers, some of whom would be seen as critics rather than allies of the big banks.

Even so, when a party becomes as dependent as the Tory Party has apparently become on a group of individuals and institutions with a number of identifiable collective interests - their shared concern about the impact of European financial services directives would spring to mind - it becomes more of a challenge for a prime minister to demonstrate that he is governing for all.

If Mr Cameron has any doubt about the irksomeness of that challenge, he need only ask the advice of Mr Blair.

You can keep up with the latest from business editor Robert Peston by visiting his blog on the BBC News website.