Outside Lincoln station a taxi driver improbably claiming his name is Richard Wobblegob says: “Honesty, that’s what we want. A bit of honesty.” He’s sick of politicians, the slippery, grasping lot of ’em. Wobblegob is clear about one thing, though: he won’t vote Labour any more. “They’re lying bastards. And I wouldn’t vote Conservative. Don’t trust them, they’re not for the working man. Think I might go for UKIP.”

After feckless MPs and economic shambles, Wobblegob’s concern is immigration — and UKIP’s stance on the subject is pretty clear. It doesn’t want any, at least not for five years. Nor do the English Democrats or the BNP, who also have candidates standing in Lincoln.

For the past two elections, immigration has been the issue that dare not speak its name. Anyone questioning the number of people coming to live in Britain was crudely accused by Labour of racism; the Tories, fearing rivers of electoral blood, ran scared.

Yet it is an issue the public wants debated. Today’s Sunday Times/YouGov poll shows that 53% of people believe there has not been enough discussion of immigration in the campaign so far. And 76% believe the number of immigrants coming to Britain is “far too high”.

In many ways Lincoln, which has mirrored the national result in elections since 1974, is an island within an island. Moated by fenland, it has a castle and cathedral on a hill, with attendant twee shops and ye olde Primark and Fat Face in a smart shopping centre. Further out lie tattered estates of Victorian terraces.

There isn’t an investment banker for miles. Instead, low-paid agricultural and processing work predominates, pulling in thousands of migrants from eastern Europe. Are they a boon or a problem? What do the locals think?

The first person I approach in the high street is a dark-haired young woman in sunglasses and black jeans, accessorised with an infant in an all-terrain buggy. Will you be voting in the election, I ask?

“Zorry. No spik Inglis. Rushan,” she says. She’s from Latvia. Nearby is Pete, supervisor of the local public conveniences. He’s worried about Gordon Brown spraying money all over the place, partly on migrants.

“I’m not opposed to people from abroad. If they come to work here, that’s all right,” he says. “It’s those that come across and sprout at taxpayers’ expense that are a problem. Why should they be allowed to do that?”

Others suspect the influx of eastern Europeans has depressed wages and snaffled jobs. The obvious person to ask is a young blonde woman hovering outside the Staffline employment agency. Are immigrants taking jobs from locals?

“I don’t know,” says Sandra, 19. “I’m from Lithuania.” Turns out she’s the receptionist in the employment agency. She works five days a week there, does two days waitressing and studies animation in her spare time. The British, largely unacquainted with pay rates in Vilnius, are not keen to compete.

At Richardson’s second-hand car lot, in the poorer end of town, a twentysomething called Simon is attending to a silver Vauxhall. He’s in little doubt about the impact of migrants: “It’s got to affect some people, some jobs. Supply and demand, innit.”

Is he going to vote? “Possibly. Possibly Tories. I’ve had enough of Labour.”

Then this Mr Ordinary Bloke, with no obvious tattoos or mental deficiencies, says without any prompting: “Or we could all vote BNP. I’d be happy to vote for them. Everyone’s so p***** off it makes the BNP worth voting for.”

Labour has itself to blame for the suppuration of such sentiments. Official figures show that it let immigration rip once it took power. In the early 1990s, long-term net immigration rarely rose above 50,000 a year but in 1998, after Labour’s first year in office, it leapt to 140,000 and hit 174,000 in 2001. It peaked at 245,000 a year before falling slightly. The latest figures show that 590,000 people arrived to live in Britain in 2008; net immigration only fell to 163,000 because 427,000 other people emigrated.

Since 1997 about 3m immigrants have arrived and the population is now 61m. The Office for National Statistics projects that the population will go on rising to 70m, with 70% of the increase caused by immigration.

Beneath the headline figures, the make-up of the country is rapidly changing. In 2008, for example, many more British citizens emigrated than returned to the UK, and many more EU, Commonwealth and other foreign nationals arrived than left. More than 500,000 arrivals in 2008 were non- British citizens.

The impacts are hotly disputed. For years Labour claimed migrants brought economic benefits. More people plus more work generally means the overall economy grows. But is anyone better off after taking into account the increase in population?

According to a recent study by Oxford Economics, GDP per capita did rise during Labour’s first two terms, but it fell in the third. GDP per capita is now lower in real terms than in 2005. Even The Economist, a fan of cheap and mobile labour, concluded last week that “there is little sign that wealth per person increased much” as a result of immigration.

The rise in the number of foreign-born people has almost matched the rise in the number of jobs, according to some calculations, leading to claims that 98% of new jobs have gone to migrants. Although this is disputed, the Trades Union Congress concedes that 50% of jobs created since 1997 have probably gone to non-UK nationals.

Services have also come under pressure in areas with large numbers of new arrivals. Council leaders in Slough, Peterborough and Boston have complained that local budgets and amenities are under “enormous strain” because official figures do not reflect their real populations.

Doctors, hospitals and schools all face challenges. In more than 300 primary schools, 70% of pupils have English as a second language, according to Migrationwatch UK, a group that campaigns for greater control of immigration.

In January two independent councillors from Peterborough wrote to Gordon Brown expressing their concerns over the pressure on schools in their area. They received no reply.

The election candidates in Lincoln gathered on Wednesday evening for a public debate at a hotel on the outskirts of town. After skirmishes over local measures, the meeting burst into life with a question on immigration. What should be done about it?

The UKIP candidate, Nick Smith, at least had the merit of honesty; at one point he likened himself to a “prat”. Nevertheless, he won applause from a minority for wanting to freeze immigration.

The English Democrats candidate, Ernest Charles, had a rum-barrel chest and Pugwash beard and, even before he announced it, you knew he had spent 36 years in the Royal Navy. When ill-informed on a topic (not uncommon) his policy was straightforward: repel immigrants. He’d scuttle the country rather than let it fall into enemy hands. More applause from the minority.

The Liberal Democrat, Reginald Shore, was a likeable man with good intentions and a policy spun from 100% pure new wool. He was very definitely for and against immigration, under certain circumstances, up to a point.

With the BNP absent, that left Gillian Merron, the sitting Labour MP, and her rival Karl McCartney of the Conservatives. Merron, an MP since 1997 and a minister since 2006, has been part of the government that presided over record immigration. All she could do was bluster about Labour’s belated attempts at control being “firm but fair”, as Brown himself did in Thursday’s television debate.

By contrast, McCartney was able to sound clear on this issue. “The Conservative party has said there will be a limit on immigrants,” he said. Not a ban, a limit. It seemed to get general approval.

In a seat the Tories should capture with a 4.8% swing, McCartney ought to be a winner, even though he has something of the 1980s night about him — a hint of estate agency, perhaps — that seems to make floating voters suspicious. Will the fringe parties detract from the Conservative vote, especially on immigration?

It’s not that simple, according to Colin Rallings of Portsmouth University. Yes, UKIP does tend to take votes from the Tories, but at the same time the BNP often takes votes from disaffected working-class Labour supporters. Both main parties are likely to be squeezed by fringe groups, with neither gaining a clear advantage.

Since both the Conservatives and Labour, it seems, are happy to avoid campaigning on immigration, Wobblegob may have to wait for his honesty. Once again immigration may end up the big issue the main parties would prefer to ignore.