I’m a remainer, but there’s one result of Brexit I can’t wait to see: leaving the EU’s common agricultural policy. This is the farm subsidy system that spends €50bn (£44bn) a year on achieving none of its objectives. It is among the most powerful drivers of environmental destruction in the northern hemisphere. Because payments are made only for land that’s in “agricultural condition”, the system creates a perverse incentive to clear wildlife habitats, even in places unsuitable for farming, to produce the empty ground that qualifies for public money. These payments have led to the destruction of hundreds of thousands of hectares of magnificent wild places across Europe.

It is also arguably the most regressive transfer of public money in the modern world. Farmers are paid by the hectare for owning or using land; so the more you have, the more you get. While in the UK benefits for poor people are capped at £20,000 (outside London), these benefits for the rich are uncapped. Some landowners receive £1m or more. You don’t even have to live in the EU to take this money: you just have to own land here. Among the benefit tourists sucking up public funds in the age of austerity are Russian oligarchs, Saudi princes and Texas oil barons.

It is hard to discern any just principle behind an occupational qualification for receiving public money. Some farmers are poor, but seldom as poor as rural people who have no land, no buildings and no jobs. Why should one profession be supported when others aren’t?

Yet even farmers have been hurt by these payments. European subsidies have helped turn farmland into a speculative honeypot, making it highly attractive to City financiers. The price of land has more than doubled since payments by the hectare were introduced, pushing it out of reach of most farmers. By reinforcing economies of scale, these subsidies have driven out small farmers and accelerated the consolidation of land ownership.

Though we have paid enough money to have bought all the farmland in this country several times over, we have not acquired any direct democratic control over the land: farming, however it might alter landscape features, remains outside the planning system. The system amounts to taxation without representation.

So you might have hoped that this would be a hot topic, surrounded by fierce debates about what should best replace this outrageous boondoggle. But, as the agriculture bill receives its second reading in the House of Commons on Wednesday, there is scarcely a murmur of either enthusiasm or dissent from the main opposition parties. The government’s proposals are a major improvement on the current system. It intends that farmers should be paid for protecting wildlife and ecosystems rather than for owning land. It wants to use subsidies to improve the health of the nation’s soils, the quality of its water and the character of its landscape. It encourages collaboration between different land managers – woefully lacking in our incoherent approach to environmental protection. But there is much to be challenged.

The first problem is that the government proposes to use public money as a substitute for regulation. Much of its new system amounts to payments for not mugging old ladies: rewarding people for not doing things they shouldn’t be doing anyway. Strong regulations, with proper monitoring and enforcement, would keep the soil on the land and nitrates out of the water without the need for this protection racket.

Yet, even as the government proposes to splash our money around, its regulatory agencies are collapsing. Natural England, like Natural Resources Wales, is in meltdown. A leaked document reveals that the government has abandoned even its pathetic target of protecting 50% of our sites of special scientific interest (threatened by farming, above any other industry). Nearly half have not even been inspected for six years. On the day Michael Gove, the environment secretary, announced his new payments plan, he also promised to find ways of reducing or removing farm inspections.

Nowhere is this replacement of rules with money more preposterous than when applied to farm animal welfare. The government acknowledges that standards should be raised. But instead of doing so through legislation, it proposes “targeted payments” for farmers who treat their animals well. Why should animal welfare be a matter of economic choice?

It is also hard to see how its policies would defend small farmers. The European system has been a disaster for them, but will this be any better? The question is sharpened by the government’s ambition to strike a US-UK trade deal, which is likely to sacrifice farming in return for concessions on financial services. Any US government, which has much lower food and welfare standards, will want a deal that lets it sell its disgusting farm products in the UK. If this happens, only the biggest and meanest farmers here will be able to compete.

The evidence from New Zealand, where all subsidies were stopped in 1984, is mixed. Since then, livestock farms have consolidated, but the number of small horticultural farms and vineyards has risen. I want to see opposition parties press the government to do two things. First, to promise that any US-UK trade deal will exclude food and agriculture altogether, even if this means no deal. Secondly, to ensure that supermarkets, which exercise monopsonistic power (too few buyers), pay a fair price to the farmers they currently exploit.

I would argue that payments for environmental goods should be reserved for those that didn’t exist before, while existing wildlife habitats are protected through regulation. I also believe that farmers should seek planning permission before changing a field boundary, ploughing a meadow or felling an orchard.

But I’m less clear about whether there should be a special support payment for small farmers, as some people argue. How would we distinguish between those who owe their living to farming and those who have bought their land as a hobby? Why should small farmers receive this money when small builders do not?

Perhaps we need an entirely different approach. How about expanding the stock of county farms (publicly owned land), which has been steadily shrinking as a result of government cuts? Where the land is suitable, county councils could divide up their farms and offer tenancies to small farmers at below-market rates. This might be a better way of supporting genuine farmers with public money. And how about a community right to buy land, of the kind now exercised in Scotland?

I don’t have all the answers, and I doubt anyone else does. But I do know that good policy depends on constant challenge and debate. And so far, there hasn’t been enough of either.

• George Monbiot is a Guardian columnist