Take a walk through the gothic halls of Westminster, the lobbies and the bars, and it looms over every MP and every conversation — enormous, dark and terrifying. The unavoidable prospect of a general election, almost certainly next year, is at the back, if not the front, of everyone’s mind.

Moreover, after years of (new) Labour rule, every sector is wondering what a possible Conservative government might be like. Not least retailing. Here, perhaps, is an industry that can think fondly of the days when the party in power was led by a grocer’s daughter who introduced Sunday trading and oversaw the rise of the supermarket giants.

But then again, perhaps not. In an interview with The Times last week, Zac Goldsmith, the environmentalist, prospective Conservative candidate and an adviser to David Cameron, the Tory leader, issued a stinging rebuke to the supermarkets that might offer a flavour of future policy “Supermarkets dominate the retail sector to such an extent that we don’t really have healthy competition”, he said. “Tesco’s market share is borderline monopoly. The effect is that neither producers [farmers] nor consumers have real bargaining power. It’s too easy simply to say that customers can vote with their feet, but the truth is supermarkets decimate the high street, destroy competition and effectively create dependence. I think that does need to be addressed.”

Not the sort of tune that will be music to the ears of Sir Terry Leahy. The chief executive of Tesco has railed against government intervention, whether over environmental fears or concerns over the supply chain. He argues that the fight against global warming should be based on informing consumers so that they can make green choices, rather than on regulating retailers. He said in a speech last month: “Each ‘bleep’ of the barcode sends a signal down the supply chain. Produce more of that product, or in the case of a product you [the consumer] have not chosen: ‘Change what you produce.’ Give consumers more information about products’ carbon footprints and they will buy greener products. And when that happens, the supply chain will turn green.”

Tesco and Sainsbury’s are on a collision course with a prospective Conservative government. The Tories are campaigning for standardised country-of-origin food labelling, which they say has been opposed by Tesco and Sainsbury’s (Waitrose and Marks & Spencer have both backed the campaign). The Conservatives say if an agreement is not reached, they will introduce legislation. The Tories are also backing the introduction of a Supply Chain Ombudsman, which is opposed by the “Big Four” supermarkets.

Nick Herbert, the Shadow Environment, Food and Rural Affairs Secretary, said: “Of course we believe in the market and the power of consumer choice. But I don’t think the market is working properly or fairly when you have such strong market dominance.”

When the country was run by a prime minister who claimed to have learnt the principles of economics working in her father’s shop in Grantham, the Conservatives did not have to work hard for the majority of retailers’ votes. The gulf between the Conservatives today and Britain’s biggest retailers suggests that those old certainties have been erased.

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