David Prosser: Britain's tawdry tax deal with Switzerland is a charter for tax evaders

Outlook Just how pleased should we be that George Osborne has persuaded his Swiss counterparts to pay some compensation for the fact that billions of pounds of British tax dodgers' money is parked in secret bank accounts in their country? Well, about as pleased as we would be if someone had robbed a British bank, fled to Switzerland and then got away scot-free apart from the inconvenience of the local authorities handing back some of the proceeds.

One understands the pragmatism of this deal, which will see Switzerland pay the UK around £380m upfront, in lieu of unpaid tax by British account holders in the country, with the promise of more to come.

It recognises the difficulty of either tracking down those tax evaders who have stashed their money overseas or forcing the Swiss to give them up. Mr Osborne seems to have taken the view that something is better than nothing.

It is, however, a thoroughly unhappy compromise. For one thing, it is deeply unfair on law-abiding British taxpayers who hand over every penny of tax they owe and would not dream of trying to hide their wealth. That we are giving up on trying to identify those who break the law simply because we're getting something back from them via the Swiss – but certainly not everything they owe – is a betrayal of honest taxpayers and an incentive for more people to evade paying tax.

And for another thing, the deal is unfair on Britain's banks (an industry the Treasury is usually quick to defend). We have now accepted that Switzerland's financial sector has an unfair advantage over our deposit takers, because British customers are getting away with paying less tax there on their money than here. It's a reward for colluding with criminality.

Then there are the people who have already come forward under HM Revenue & Customs' previous offers of lenient treatment. It turns out the treatment would have been even more lenient if only they had not been so honest.

Finally, we should worry about the precedent we are setting with this deal. Christian Aid, for one, thinks the arrangement will make it far tougher for less wealthy and politically influential nations to chase their own tax-evading citizens – and thus the recoup the revenues they need even more desperately than we need ours.

Switzerland does not have an automatic right to banking secrecy that it is entitled to protect at all costs. This behaviour is not acceptable from a country that claims to be a good international citizen.

Nor do other countries accept that the UK's pragmatism is the only way to get results. The US authorities, for example, havechosen to take on Switzerland's banks one by one and they have won much greater levels of disclosure from them. We should do the same, rather than letting tax evaders get away with it.