Most discussions around immigration end in bitterness and antagonism because each side has a preconceived idea of whether immigration to Britain is a positive thing or a social ill. This is not unlike most political rows; yet it can feel like there is a rarely a middle ground on immigration. In every argument statistics are deployed, not for their accuracy, but on the basis that they will brutally strike down the argument of an opponent.

The sheer degree of bad faith has been magnified by the impending EU referendum. Immigration is one of the issues that will decide the referendum; yet it is incredibly difficult to get a true picture of the impact immigration has had on Britain since the accession of former Eastern Bloc countries to the EU in 2004.

I don't claim to be impartial – I lean toward supporting free movement - but in recent months my faith has been tested by what you might call the 'facts on the ground'.

To cut a long story short, in the process of conducting research for a book I recently worked undercover at one of the world's largest multinationals. The warehouse is situated in Rugeley, a former mining town in the Midlands, and around 80% of those I worked with were Romanian migrants. My job was to pick orders off the shelves for the firm's customers – dull and laborious work with insufficient break periods and barracks-like discipline.

I finished my four weeks in the job with heavy legs and suppurating feet, but also with a better understanding of the impact EU migration (there are now a record 2.1 million EU workers in Britain) has on unexceptional little English towns like Rugeley.

All of the following points are grossly obvious if you work in one of these jobs, but less so if immigration means no more to you than a set of figures on a balance sheet and a Spanish barista at Starbucks.

1) Most of the lowly work was done by Eastern Europeans

Around 80% of the really wretched jobs were done by Romanians.

From the perspective of the employer, the typical refrain when presented with this sort of data is 'We can't get English people to do the work'/'the locals don't want them'. The implication is that the British working class are coddled and lazy.

The implication is that the British working class are coddled and lazy.

In practice it's likely that most British workers have minimum standards relating to the work they are willing to do – standards which many of the precarious and poorly-paid jobs our economy now relies upon do not meet. That was certainly true of the local people I talked to in Rugeley. As Alex, a former miner from the town told me with respect to the work I was doing: "I wouldn't do that work. I'll make no bones about it: I wouldn't do it because I'd fall out with them [the managers] over how they treat people."

The fact that a growing number of British people are unwilling to be treated like animals by unscrupulous employers is commonly viewed as in some sense shameful, when really it is a sign of progress.

2) Most of the Romanians told me they planned to go home

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Most of my co-workers said they planned to return to their country after a short period in England earning money – one, two maybe three months. It is of course impossible to verify this – they may simply have been giving this answer in response to what they interpreted as the potentially hostile questioning of an Englishman (me). It's very hard to track individual migrants, but the fact that the net migration figure – those coming in minus those leaving the UK – remains high would suggest that lots do ultimately end up staying.

3) Job expectations were lower, which matters to everyone

The company I worked for – as well as the agencies it used to find employees - got away with a good deal more because it presided over a largely foreign workforce. Most of the people I worked with had little grasp of their employment rights. We didn't receive employment contracts and my Romanian colleagues assumed that this was normal. One Romanian told me that he was fearful of complaining because he thought he might be deported. Another was underpaid and I had to phone payroll on his behalf to complain because his English was poor.

I saw many things that simply would not fly if they had been done to British nationals.

For all the partisan statistical analysis claiming to show that migration has little or no impact on wages, anyone who has done this sort of lowly work (as opposed to fulminating about it from a warm office in London) knows that a never-ending supply of docile and fearful workers has a blunting impact (though there is a debate to be had as to what extent) on pay and conditions.

If you can turn labour on like a tap - if you have a large reservoir of workers who are desperate for any work that you will give them - collective bargaining power is invariably weakened. I saw many things that simply would not fly if they had been done to British nationals.

The other point worth making is that it is far harder to unionise people who only plan to stay in the UK for a short period of time. They don't see any purpose in rocking the boat and potentially being thrown out of work. After all, it's only for a month or two.

4) Migrants were not 'stealing our jobs'

In a growing economy there is never a finite number of jobs anyway; but the notion that migrants were stopping locals from getting jobs was, in Rugeley at least, a fiction. This goes back to point 1. There was no local clamour for these jobs. There were almost no English people at the various open inductions I attended and ones I did work with quit within a month.

5) At some point you probably have to give EU migrants political rights

Many formerly working class jobs are today done by foreigners who lack political rights in the UK. According to Oxford's Migration Observatory, around 29% of foreign-born male workers are employed in elementary and processing occupations compared to 21% of their UK-born counterparts. A growing section of Britain's working class is thus almost completely politically disenfranchised (they can vote in local elections).

A growing section of Britain's working class is thus almost completely politically disenfranchised

This throws up a new challenge for the left; put some sort of lid on EU migration or expand political rights in this country to include EU workers.

As things stand, the British working class is slowly being replaced by a foreign-born labour force. In a superficial sense this is neither here nor there; but if the people who toil in British factories have no say over the political direction of the country they live and work in, it will invariably create a distorted politics in which the only voters are middle class voters. Universal suffrage will, in practice, no longer exist.

You can of course infer from all of this what you will. As I say, I don't think that reining in free movement is the answer. But I do wish that liberals would show a proper interest in the impact immigration has on industrial relations, rather than simply playing a parlour game of reeling off the calculations of effete academics cocooned in offices at progressive think-tanks in London.

Educated people should be capable of exploring the impact migration has on the relationship between labour and capital without endorsing draconian anti-migration legislation.

James Bloodworth is the author of The Myth of Meritocracy