Mark Thatcher is bad for Howard, but he's not so good for Blair, either

The latest instalment in the Improbable Adventures of Mark Thatcher must be unwelcome to both Tony Blair and Michael Howard as they prepare for the new political season. Howard's difficulty is perhaps more obvious than the Prime Minister's. The Conservative leader needs this kind of reminder of his party's past in the same way that he needs cartoonists to be reminded that his family come from Transylvania.

The latest instalment in the Improbable Adventures of Mark Thatcher must be unwelcome to both Tony Blair and Michael Howard as they prepare for the new political season. Howard's difficulty is perhaps more obvious than the Prime Minister's. The Conservative leader needs this kind of reminder of his party's past in the same way that he needs cartoonists to be reminded that his family come from Transylvania.

Sir Mark comes with a whole baggage train of associations with the get-rich-quick underside of his mother's period in office - even the hereditary baronetcy is a white stick, an indicator of her blindness to his shortcomings. Few people remember now the details of his alleged role in securing contracts in the Middle East - it was never proved that he did anything illegal - but the impression endures that he exploited his mother's position for personal advantage.

Along with the alleged involvement, not quite categorically denied, of Jeffrey Archer, the yarn about Equatorial Guinea serves to remind people of the Tory reputation as a party of lesser financial probity than its rivals. We may not be able to follow every twist of the (alleged) plot, but we are reminded that top Tories used to hang out with some rather questionable people.

In many ways, the Conservatives' image as a party of financial sleaze was undeserved. The activities of a few backbench Tory MPs had a disproportionate effect in the 1990s. Partly for historical reasons, dating from the time when being an MP was a part-time voluntary occupation of the landed and professional classes, the party tended to take a relaxed view of the financial interests of backbenchers. That resulted in humiliation for John Major in 1995, when he rejected the advice of Lord Nolan that the outside earnings of MPs "connected with their being MPs" should be disclosed. Blair accused him of bowing to the "squalid monied interests of the Conservative Party" and the government went down to defeat in the House of Commons because 23 Tory MPs thought that, having appointed Lord Nolan to tighten the rules, they should accept his findings.

In other respects, too, the Tories were less stringent about financial probity than Labour. They kept the sources of party funds secret when they were in government. When they were found out, in the case of a donation from Asil Nadir, the fugitive tycoon, they refused to give the money back. Blair legislated for openness and when he was found out, changing policy at the behest of Bernie Ecclestone, the Formula One billionaire, the Labour Party returned the money.

But the difference between the two parties was one of degree rather than of kind. As Democratic Audit, a civil rights research group, points out: "British politics are relatively uncorrupt by the standards of the larger European nations."

In fact, Thatcher's indulgence of her son was always treated rather indulgently, when the financial interests of a prime minister's family should be judged harshly. But John Major's personal integrity was never questioned, and the conduct of Conservative ministers tended to be at the sea-green end of the spectrum. Blair may have overdone the rhetoric, implying on occasion that he and all Labour MPs had taken vows of poverty and chastity. In practice he continued a process of greater openness and protection against conflicts of interest that was already under way. Democratic Audit, which is not naturally sympathetic to New Labour, gives Blair credit for incremental but significant progress. The hopes of the Freedom of Information campaign have been mostly disappointed, but the new regime of rules on standards in public life has been a step forward.

Unfortunately for Blair, greater openness - the disclosure of party donations of more than £5,000 a year - has since 1997 only helped close the gap in perception and reinforce the impression that Labour is just as bad as the Tories. Perhaps it is inevitable that the reputation for probity of a party in power will become tarnished over time. But had it not been for the new rules, there might never have been a fuss about Lakshmi Mittal, the Indian steel magnate, or about Paul Drayson, supplier to the Government of smallpox vaccines. Equally, Blair's cynical continuation of the Tory policy of giving peerages to party donors (including Drayson) would not have been exposed to such scrutiny.

What a relief it must be for the Prime Minister to have the headlines stolen by people who remind us that it was actually worse in the bad old days.

And yet ... the trouble with Mark Thatcher from Blair's point of view is that he is also a reminder that perceptions of politicians are shaped by their families. John Major, Jimmy Carter and Bill Clinton had embarrassing brothers. Tony Blair has a brother and sister so self-effacing that many people are not aware of their existence. But he also has a wife of whom everyone has heard and on whom everyone has an opinion. And she has a book on prime ministerial spouses coming out next month. Mark Thatcher's alleged role in an alleged coup that reads like a cross between Capt WE Johns and Jeffrey Archer is hardly the best curtain-raiser for Cherie's attempt to prove that politicians' relations can make a constructive contribution to public life in their own right.

Most of the perception of Cherie is grossly unfair, the product of an unrelenting campaign by the Daily Mail and other newspapers to portray her as a freeloader. The attack on the Blair family's holiday arrangements this summer was particularly fierce, with the word "freebie" liberally deployed, despite the fact that the Blairs make donations to charity in lieu of payment. It would seem that it is wrong in principle for politicians to accept hospitality from anyone rich. But if the Blairs did try to go on a package holiday to Majorca, it does not take much imagination to predict the security complications, including attempts by News International employees to try to get jobs in their hotel.

Equally, despite heroic efforts, the Mail has never found anything in Cherie's financial dealings that even begins to compare with Mark Thatcher's exploitation of "Mumsy". The worst Cherie ever did was to allow her friend's conman boyfriend to help negotiate the purchase of two flats in Bristol as a family investment.

Attempting to justify the hounding of her, the press routinely describes Cherie as the most powerful woman in the country. As Cherie may remind us in her book, that may have been true of Emily Palmerston, or even Lucy Baldwin, credited by her daughter with supplying Stanley with all his "ambition, push [and] drive". But Tony needs no such chivvying.

The Mark Thatcher story ought to remind people that this prime minister has been slightly but importantly more open and honest than his Conservative predecessors. Instead, it might just reinforce the common prejudice that all politicians and their families are up to no good.