If trade unions are not going to go on strike now, their leaders might as well clench their fists for the last time, bow solemnly before the sisters and brothers, and perform the last rites on their movement. The longest fall in wages for generations; pay packets for many public sector workers down by a fifth in real terms; and, despite politicians' deceitful mantra that work is the route out of poverty, most of Britain's poor consigned to low-wage jobs. An increasingly casualised, hire-and-fire workforce is being forged, manned by an army of zero-hour contract and self-employed (often "self-underemployed") workers lacking basic rights like paid leave; and the vast majority of new jobs in David Cameron's Britain in industries paying less than £7.95 an hour. Throw in cuts to in-work benefits, attacks on pensions and VAT rises, and the rationale for workers to fight back is surely unanswerable.

That will not be the case presented in most of the media when hundreds of thousands of workers take part in co-ordinated strike action on Thursday. This column will remain one of the very few pieces supportive of the strike to be published by the mainstream media. I don't write that as an act of self-congratulation, but simply to point out how ideologically charged and biased our media is. Trade unions are Britain's biggest democratic movement, representing 6.5 million workers – more than nine times the combined membership of the main political parties – and yet they are treated by the media as though they have almost no legitimate place in public life. On the rare occasions they are granted media coverage, their elected leaders are invariably described as "union barons". Surely it is only unelected, unaccountable figures like media owners who should be called barons.

Cover your ears for the screeches of outrage over a day of disruption by a media largely uninterested in the never-ending disruption caused by falling living standards. There will be non-stop complaints about strike ballot turnouts, stoked by the likes of Boris Johnson – narrowly elected London mayor on a 38% turnout – and Tory politicians who championed police crime commissioners elected with an average turnout of 15%. If our rulers were really interested in boosting turnout they would allow workplace-based balloting, but they are not.

Another key plank of anti-strike propaganda will be the politics of envy. Struggling people are relentlessly encouraged to envy each other rather than to be angry at those with power, who are responsible for their ever-deteriorating plight. Private sector workers are worse off, goes this line of argument, but you don't see them downing tools en masse, unlike those pampered public sector workers with their cushy perks. This is the logic of the "race to the bottom". It is all based on myth, given that the public sector has a higher ratio of professional workers like judges, university lecturers and senior civil servants, and the pay figures are also distorted by high wages in bailed-out banks like the Royal Bank of Scotland, which have been reclassified as public sector institutions. A quarter of local authority workers, for example, languish on poverty wages.

Labour is often demonised, sometimes with the complicity of its own leaders, for being in the "pocket of the unions". This is odd given Labour leaders' commitment to the Tories' public sector pay freeze, their acceptance of cuts and their timidity even when it comes to popular policies like public ownership of rail. Labour should speak of its pride in being backed by a movement of dinner ladies, supermarket shelf-stackers and care assistants – union funding is, after all, the cleanest money in politics. But where is the never-ending scrutiny of a Tory party bankrolled by bankers, hedge funds, legal loan sharks, and secretive private interests?

When it comes to unions, there is a chasm between the elite and popular attitudes. How it must rile politicians that, while only 18% of the public believe them to tell the truth, and just 34% of us believe business leaders, trade union officials are trusted by 41%. Those who relentlessly dismiss unions as outdated vested interests must be frustrated to learn that 78% believe trade unions are essential to protect workers' interests; and those portraying unions as being run by extremists and militants may huff as they find just 23% of Britons agreeing and 60% disagreeing. Despite the media's best efforts, 49% of us believe that big business poses a greater threat to the public than trade unions, with just 13% dissenting.

In truth, we all suffer because of trade union weakness. The great squeeze in wages long predates the financial crash: from 2004 onwards, the bottom half of workers found that their pay had stopped growing, and for the bottom third pay in real terms began to fall. That increased the burden on the taxpayer as billions more were spent on tax credits to compensate. Many workers relied on cheap credit to maintain their living standards, helping to win Britain the dubious honour of being one of the world's most indebted nations. Wages began sliding even as corporations posted record profits – but there were no strong unions to compel them to share the wealth.

As a 2011 US study found, the decline of unions is behind a fifth to a third of the growth in wage inequality across the Atlantic. Last week, Kate Pickett and Richard Wilkinson, co-authors of The Spirit Level, published research for the Class thinktank that fleshed out the link between a weakened labour movement and growing inequality.

That doesn't mean our hunted unions are beyond scrutiny. While most public sector workers are unionised, just 14% of private sector workers are members. All too many supermarkets and call centres are virtually union-free zones. Yes, it is hard to organise because of a law tilted in favour of bosses, and because insecurity leaves workers less likely to remain in the same job. But as early 20th-century unions adapted their organising model to recruit unskilled workers, today's unions must focus their efforts on the ever-expanding service sector. Private sector union membership has grown from a low base for three years running, but unions must expand their efforts to organise in the community as well as the workplace, as the likes of Unite have done.

Come Thursday, hundreds of thousands will sacrifice a day's pay to take a stand. They will be ignored or demonised as they do so. But they should remember that they are not just speaking for themselves, but for the millions expected to pay for a crisis caused by the vested interests who fund the Tories. Who knows – they may give courage and inspiration to others to get off their knees, too.