Yasmin Alibhai-Brown: In a sea of corruption we only catch the small fry

I met Derek Conway recently and there was no tremor of culpability

You can't blame Boris Johnson or Ray Lewis for being more baffled than mortified at what has just come to pass. "What is the big deal?" the chaps must be muttering to themselves. In the surf waves that crash in of political corruption and frequent transgressions, the scandal of the London Deputy Mayor is but a droplet. So, Lewis was investigated by the Met (three times, mind) in 1997 for alleged blackmail, then in 1999 after being accused of theft, and there were whisperings about sexual harassment. Not good for a former vicar, deputy prison governor and self-proclaimed saviour of black boys, admittedly, but was it really necessary for him to be pushed off so ignominiously?

Many don't think so and are indignant. They include Iain Duncan Smith, Francis Maude and Stephen Norris. Lewis may have been economical with the truth but, says one friend, the man was never crooked, he just had an "imprecise view of the world". What an imaginative excuse. The shady and shifty should use this one the next time they face stern Milords. Even Ken Livingstone, who stalks Boris like a vengeful ex-spouse, thinks Lewis, like everyone, just has a past.

Other prominent figures were self-righteously outraged when James McGrath, Boris's chief-of-staff, departed last month after "unfortunate" throwaway (not giveaway) comments he made to a black journalist suggesting that Caribbean Britons who said they would go back "home" if Boris became mayor could freely do so. These creatures of power and influence have been swimming in polluted waters and they cannot smell, see or touch the dirt. The idea of ethics and temperance in political life has receded so far that it is invisible to their eyes. When censured, therefore, it feels to them as if they are being sharked upon by a vicious press and public.

I met Derek Conway recently and there was no tremor of culpability anywhere on the jolly old geezer. His well-paid, indolent boys are even more brazen. And now Conway says MPs should get a £200,000 salary to attract exceptional minds like his, I guess – indispensable men of character. The Wintertons are similarly blasé about robbing the taxpayer by making a claim of £66,000 on a house which had no outstanding mortgage. Now we are paying for new rented quarters for this hideous couple, one a knight of the realm.

George Osborne, it has been revealed, received thousands of pounds for making a speech at a private business function. New Labour doesn't dare to condemn "Tory sleaze" because on its watch sordid deals and favours have become the norm. Under the Blairs, corruption got worse than under the bad old Tories and Brown has not yet shown he understands how much cleaning up there is for him to get on with.

"Poor me" Cherie still can't see why we despise her grossly excessive lifestyle and her holidays with Berlusconi. Wannabe deputy leader Peter Hain is being investigated for his fundraising methods. For some inexplicable reason, super-generous donations from friends of Israel remain unexplained. And now MPs, mainly Labour, including Jacqui Smith, and Andy Burnham and Peter Kilfolye (so-called man of the people) voted to keep all the their unfair perks, including the staggering John Lewis list. An independent commission suggested they mend their wicked ways and this lot have simply said fuck off.

Remember Elizabeth Filkin, the fine Parliamentary Commissioner for Standards? They got rid of her fast because she challenged this lax political culture. She didn't understand, apparently, that everyone was at it, the so-called "Dagenham defence", used by Ford car workers when caught smuggling out stolen goods. In 2006, a weary Alistair Graham, chairman of the Committee for Standards in Public Life, also had to go because he took his job seriously.

In Martin Bell's book, The Truth That Sticks, he writes: "Standards of conduct have fallen shamefully. Now the time has come for them to rise again. Reform is not only due, but overdue." The civil service, quangos, public service trusts and charities do not flout rules and corruption is not tolerated. But politics more and more swims free from constraints, contaminating itself and good people who became MPs who still try to do the right thing. In 1995, the Nolan report defined seven probity principles: selflessness, integrity, objectivity, accountability, openness, honesty and leadership.

In 2008, this list is as archaic as the ten commandments. Anything goes in politics. That being the case, you can see why it is so very hard for Lewis and Boris, and was previously for Ken and Lee Jasper. Why punish only small fry swimming with the big fish and the tide of filth? A fair question, and one that will not be silenced by the resignation of Lewis.

y.alibhai-brown@independent.co.uk