Leading article: The corrosive Tory infatuation with wealthy businessmen

David Cameron has changed the Conservative Party in numerous ways.

But what the Tory leader has not reformed, nor shown any inclination to reform, is his party's relations with rich businessmen who have a questionable attitude to paying tax in Britain. Mr Cameron, notoriously, put the non-domiciled billionaire Lord Ashcroft in charge of his party's marginal constituency-targeting strategy at the last election (although the peer has since become a full British resident, enabling him to retain his seat in the House of Lords).

More recently, the Tory leader offered David Rowland, the property magnate and former tax exile of 40 years, the post of Conservative Party treasurer (a job the businessman turned down this week after attracting negative publicity). And it is not just in the Conservative Party that Mr Cameron seems keen on appointing wealthy businessmen. He has brought them into Government too. The retail tycoon Sir Philip Green, who transferred £1.2bn from his UK business to his Monaco-based wife in 2005, has been appointed by Mr Cameron to advise Whitehall on cutting waste. Such cosy relationships between Mr Cameron and controversial wealthy businessmen are unwise for a number of reasons. First, it is politically destabilising. The appointment of Sir Philip has been embarrassing for the Tories' coalition partners, the Liberal Democrats, who have always taken a strict attitude to full payment of tax in the UK by the wealthy. Whatever contribution the Topshop boss makes to cutting waste, it is unlikely to compensate for the political damage his appointment has already generated.

These relationships are also unwise strategically for Mr Cameron and the Government. It seems increasingly likely that the middle-class welfare state (payments such as universal child benefits and free bus passes for all pensioners) is going to be curtailed as part of the public economy drive. But while savings are being sought in most areas, when it comes to tax avoidance by the wealthy the signs seem to be pointing in the other direction. The permanent secretary for tax at Revenue & Customs told a newspaper this week that it will henceforth be adopting a less combative approach in company tax disputes as part of the Government's campaign to show that Britain is "open for business".

Mr Cameron and George Osborne tell us that, when it comes to restoring the public finances to health, "we are all in this together". But while benefit cheats are (rightly) castigated, the same attitude does not apply to the super-rich and their tax affairs. As the welfare state is ruthlessly pruned, the corporate welfare state is left intact. It would seem that there is one rule for the super-rich and another for everyone else.

We need to reform the financing of our politics so that political parties are not reliant on individuals such as Lord Ashcroft and Mr Rowland for donations and fundraising. And though the Conservatives are particularly inclined to rely on the generosity of rich men, this is a problem common to all three of the main parties. Both Labour and the Liberal Democrats have had problems with wealthy donors in recent years. Breaking this unhealthy dependency will require political leadership. Yet, sadly, Mr Cameron's behaviour is marking him out as part of the problem rather than the solution.