National Gallery assistants go on indefinite strike today. Much of the gallery will be shut to the public, at the height of a tourist season. This dispute has been worth following – not just because a great national treasure has now been closed intermittently for 52 days and counting since the dispute started, but because outsourcing long-time loyal staff is the kind of ruthless treatment the government is urging in its trade union bill.

This has been a story of shameful dereliction of duty on the part of the board of trustees, when a reasonable solution was available. What ineptitude to inflame the dispute by sacking the union rep, Candy Udwin, whose first hearing at an employment tribunal made clear she is likely to win an unfair dismissal case. Among the bankers, hedge funders, private equity dealers and accountants on the board, few appear to have management experience: one is on the board of Barts NHS Trust, a notorious calamity. There are artists and academics too, but few, it seems, with staff management skills.

That may be why they undervalue their employees. The 400 gallery assistants and visitor staff are transferred over to Securitas this week, their fate sealed. This is their last attempt to stay as gallery employees. In July they won the London living wage, but pay was not their main cause.

Many of them have worked at the gallery for decades, some are artists themselves. But once outsourced to Securitas, they can legally be moved on to anywhere else in the company, as long they get the same conditions. Securitas has contracts guarding ports and aviation, shops and offices, so someone who has for years guarded Van Goghs and guided visitors to rooms filled with Renaissance wonders could now be sent to protect an airport. When I quoted one member of staff worrying they could end up guarding a supermarket car park, the gallery’s departing director, Sir Nicholas Penny, wrote to the Guardian saying: “I want to reassure everyone we would certainly endeavour to ensure that is not the case.” But in law, there is no such protection, whatever his “endeavour”. Many staff would leave if sent elsewhere – thereby allowing Securitas to hire others on worse conditions. That’s why outsourcing is cheaper. On the Securitas website, there is an article entitled “To outsource or not to outsource?”, calling on police and crime commissioners to privatise more police functions: “The view held by some that outsourcing is more expensive than running things in house is simply not so when private security companies are able to pay their staff a lower rate.” Just so.

With its trade union bill, the government declares war on the depleted ranks of the unions.

The word for this is “modernisation”. The National Gallery announced the Securitas deal last month as part of its “commitment to modernisation and a move that will enable the gallery to operate with greater flexibility”. Here’s how the word is used by Matt Hancock, minister for union bashing, announcing an end to the “check-off” system so public employees can no longer have their union subs collected from their pay packet: “It’s time to get rid of this outdated practice and modernise the relationship between trade unions and their members.” That “modernisation” will demolish union funds if too few members set up direct debits.

That’s why as political terms “modernisation”, “reform” and “flexibility” have become toxic in Labour’s lexicon. The genuinely modern way would be to aim for “collaboration”, “cooperation” and “consensus”, with employees on company boards, working together, German-style. The National Gallery staff know full well that their gallery, like all the arts, has taken a severe cut in its grant, with worse to come: they know extra money needs to be earned from late openings for private events. They have drawn up a detailed plan at the same cost to which they say they have had no reply at all.

Sir Nicholas Penny has left behind this chaos. His statement says: “We believe Securitas is the best possible partner for us. This is the right decision for all our staff.” Yet he has just given a farewell interview to the Telegraph: “He said the recent strike over plans to contract out certain jobs was ‘a great sadness, in part because he sympathises with the union case. “I would much prefer to keep all the gallery assistants as part of the gallery. If they’re not, they don’t feel part of the institution in the same way.” In which case, who was in charge? Did Penny lose his grip? And where are the trustees? No one was available to talk to me.

Next week the new director arrives – Gabriele Finaldi from the Prado – who knows the National Gallery well from previously working there as a curator. He says: “I eagerly look forward to working with the trustees and the staff to strengthen the gallery’s bond with the public.” But the place will be half-closed. Will it be too late to unpick the Securitas deal and return to Acas, where the union is eager to present its alternative plan? He has a chance to step in and sit down to talks.

With its trade union bill, the government declares war on the depleted ranks of the unions. The moth-eaten old lions still roar, London Underground staff can cause a day or two of inconvenience, but the unions have lost most of their teeth. Since 2010 an average 647,000 days have been lost to strikes, compared to 7,213,000 days lost a year in the 1980s. Loss of power has seen pay fall while profit rises as a share of GDP. Pay keeps up only where easy-to-organise groups stick together, such as Transport for London staff – or CEOs.

The bill to ban strikes without a 50% turnout and 40% of those eligible voting yes is a shoddy ploy: few MPs muster that. Even when enough vote, employers can bring in agency workers to break a strike. Roughly half of strikes since 1997 would now be illegal.

If the government really wanted more people to vote they’d make it easy, for union members and citizens. Tories will use electronic voting for their London mayoral primary – so why do they ban it for all other elections and union ballots? Because for all but those in their own ranks, the fewer votes cast the better. They want obstructions to strike votes and obstacles for the poor, the young and low paid, just as they resisted universal suffrage in the past.

National Gallery assistants are a small pocket of resistance to the tsunami coming to sweep away the slender remaining rights of the nation’s workforce.