If you pay peanuts, you get monkeys. But it turns out that if you pay for a packet of Maltesers, you get a Member of Parliament. The baroque system of MPs' pay has finally been tipped into crisis. From the moment that pay for MPs was introduced in 1911 the arrangements were complicated and their rationale confused. Indeed, the correct remuneration has been a subject of controversy since the Middle Ages. It is long past time to settle the matter.

In the midst of a controversy in which some MPs are being pilloried for calling out an electrician or having a lavatory seat fixed, while others have clearly been gaming the tax system, it is hard to recall that paying MPs properly was long a progressive demand. Many felt that people should not be debarred from Parliament because they had insufficient means to serve. When, in 1909, the courts debarred the trade unions from funding Labour MPs, the Liberal Government finally acted and pay was introduced.

David Lloyd George, making the argument for the £400 annual payment, said: “It is not a remuneration, it is not a recompense, it is not even a salary. It is just an allowance.” These are interesting distinctions, but sadly Lloyd George is no longer in a position to explain them. In the years since his passing, more distinctions have been added. The system has become unwieldy, easy to abuse and has lost public confidence. One of the most striking features of the latest revelations is that it is quite impossible to understand why one claim was granted and another refused.

So the new system should be based on clear and simple principles. First, MPs are doing an important job and should be paid enough that high-quality people without independent means are financially able to do it. Being an MP is a public service and should not be a way to become rich. But nor should MPs earn only an average wage. Being an MP ought surely to pay as much as a GP or a secondary school head teacher. And inevitably that means that, say, deputy head teachers or nurses will feel that their MPs are getting something that they are not. The sensible setting of MPs' pay cannot be held hostage by this sentiment, however understandable it might be.

Second, accepting that MPs should be paid broadly as a head teacher or GP is paid, means raising their salary. Since 1911 there has never been a fully satisfactory way of agreeing pay rises for MPs. The pay of MPs should be placed entirely in the hands of an outside body, insulated from the ups and downs of political opinion and concerned only with the market for professionals capable of being good legislators.

Third, the additional costs allowance for a second home has outlived its uselessness. And it is very hard to eliminate one set of anomalies without introducing others. The allowance should, therefore, be abolished and the sum incorporated into MPs' salary so that they are paid £90,000 a year. They should also, like all office workers, be reimbursed for office-related travel. Such a salary would be less than in many other legislatures in developed countries. It would also bring the allowances inside the tax system.

Fourth, the correct number of MPs should be determined in a separate debate. The bill for Parliament is not exorbitant. We should not decide whether we need more or fewer MPs simply to make the maths of the salary change add up.

Finally, we should not insist that MPs give up all outside interests. Some argue that such work makes them better MPs. Let this be tested. If there were primaries, allowing voters to choose among candidates for the parties, then this assertion would be judged by voters.

Simplicity, dignity, independent rules, a proper professional salary, accountability: after 600 years, is this too much to ask?