Labour leader Ed Miliband has repeatedly pledged to end "exploitative" zero-hours contracts. We can safely assume that he does not plan to abolish exploitation in a Marxist sense - the pumping of unpaid labour out of one class by another.
To oppose such exploitation would be to oppose capitalist profit-making full stop.
Nonetheless, the pledge reflects Labour's recognition that many people suffer or fear suffering uncertainty in their working life, an issue that zero-hours contracts have come to symbolise.
A new survey by the Office for National Statistics (ONS) sheds light on the prevalence and distribution of these working arrangements.
Until now there were two widely used sources of data.
The first, the Labour Force Survey, is a survey in which a sample of employees are asked about their work.
The survey for October to December 2013 found that 583,000 people claimed to be on zero-hours contracts, up from 250,000 in the same period a year earlier.
This was reported by one Guardian columnist as showing that "the increase in zero-hours contracts has been dramatic... 137 percent between 2012 and 2013". That claim was nonsense. The survey reflects people's perception of their contract.
As the ONS makes clear, "Some of this increase is likely to be due to the increased awareness of 'zero-hours contracts' following the coverage in the media."
It points out that over half of the increase is among people who have had their job for more than a year, "and so would not be 'new' contracts".
The Labour Force Survey both underestimates the extent of zero-hours contracts and exaggerates their recent growth.
A second source of data is the Labour Market Outlook Survey carried out for the Chartered Institute of Personnel and Development (CIPD).
Rather than asking workers, they surveyed 1,000 companies producing an estimate of about 1 million people on zero-hours contracts.
The new ONS study is based on a business survey, but the ONS used a larger and more representative sample. This led to a new estimate of 1.4 million contracts - probably the most accurate figure we have.
There are a few reasons why even this number should be treated with caution. First, there is no agreed legal definition of a zero-hours contract.
The ONS defined them as contracts in which workers are not guaranteed a minimum number of hours of work, but a different definition might yield a different figure.
Second, some workers have more than one zero-hours job. The figure is for the number of contracts, so the number of workers would be a little lower.
Third, the figure only includes contracts leading to some work during the fortnight in which the survey was conducted. There are a further 1.3 million contracts where no work was undertaken.
The ONS cautions against lumping these together with its 1.4 million figure. Some will relate to people who remain on an employer's books but have found new jobs or who did not seek work in the period, for whatever reason.
But some of these "inactive" contracts probably should be added to the overall figure, increasing it somewhat.
Now, there are far too many workers on zero-hours contracts. But it is worth noting that about 95 percent of jobs do guarantee a minimum number of hours.
Contrary to claims that we are seeing the formation of a "precariat", stripped of job security and powerless to fight, most workers still experience more secure conditions that they did during periods of much more intense workers' struggle in the 19th or early 20th centuries.
This observation does not simply apply to zero-hours contracts. Currently about 6.4 percent of the workforce is in temporary employment.
But the figure ten years ago was 6.1 percent, 20 years ago 6.8 percent. Working life has deteriorated in other ways, but permanent work has proved to be quite resilient in Britain.
Of course, if our rulers can get away with making workers more "flexible" without undermining the conditions for profit-making, they will do so. But this is not always possible. Although workers depend on their jobs to earn a living, capitalists also depend on us. We are not quite as disposable as our rulers might like us to believe.
Even in the current miserable recovery from recession there is evidence of "labour hoarding" in which bosses try to hang on to workers even if they reduce hours and attack wages
They do this to retain skills, to avoid the costs associated with firing and, if things pick up later, rehiring labour, and, sometimes, to avoid sharpening antagonisms inside the workplace.
A report by the Institute for Fiscal Studies last year found "strong evidence" for labour hoarding, especially in businesses with fewer than 50 employees, where the relative costs of hiring and firing are particularly high.
There is a play off between the benefits that capitalists reap from making workers flexible and from securing a relatively stable and permanent workforce.
This is why issues such as zero-hours and temporary working affect a minority of workers in Britain.
Even where zero-hours contracts are used, they do not always reflect the casualisation of previously stable long-term or full-time jobs. About one fifth are among full-time students, who often have to combine casual work with studying.
Not all those working part time on zero-hours contracts consider themselves under-employed. According to the Labour Force Survey, only about a third wanted more hours, and, when CIPD conducted a survey of workers on the contracts, it found that about half were satisfied with not having a minimum number of hours.
None of these qualifications mean we accept Labour's feeble pledge to end zero-hours contracts only in certain "abusive" cases and only after a year of employment.
All workers should have the right to opt for a contract securing a minimum number of hours if they want it, and from day one of their employment.
Achieving this goal requires struggle - and we should fight over these issues. While socialists ultimately want to overthrow work in its current form, we are far from indifferent to the nature of work in the here and now.
By far the most effective way to challenge zero-hours contracts is through collective action in the workplace. This can mean workers striking to block their introduction, as the action at Hovis in Wigan did last year.
But there are lots of workplaces where zero-hours contracts are already in use among a minority of employees. They are used to some extent by about one in six businesses - and more than half of large businesses with 250 or more workers.
The widespread use of these contracts is double-edged. On the one hand, it can lead to feelings of insecurity, fears that such arrangements will be generalised across the workforce. This is compounded by the intensification of work and relatively low level of struggle in recent years.
If bosses can push workers around easily within the workplace, it can help create a perception that they can also push them out of the door.
On the other hand, it can also lay the basis for struggles involving both those already affected by zero-hours contracts and those who are not, in order to force employers to offer guaranteed hours of work to the whole workforce.
The areas where zero-hours contracts are most concentrated are "accommodation and food" and "admin and public services", with the latter including agency staff who, in practice, actually work in a range of other sectors.
There are also large numbers in "health and social work" and "transport, arts, other" (over 10 percent of workers), and quite a few in "education" (around 5 percent). Some of these areas have seen struggles in recent years, and in some cases there is a level of union organisation.
Of course, zero-hours contracts are not the only form of casualisation. But the argument holds more generally.
For instance, universities have been condemned for using fixed-term contracts and hourly-paid employment. The figures here are astonishing.
According to CIPD, where educational institutions use fixed-term contracts, they apply to an average of a fifth of the workforce. But these institutions are sites in which a mass of workers have been drawn together and subjected to conditions in which many have joined unions and fought in recent years.
Union leaders have rightly been critical of Miliband for not going further on zero-hours contracts. Socialists need to translate this sentiment into action on the ground.
While not all those affected by this problem will be in the strongest position to fight, enough organised and powerful groups of workers are in workplaces where zero-hours is an issue - and that seems like an excellent place to start.