As the spectre of Brexit emerges, so do the first meaningful signs of the Tory vision of “building a global Britain”. The Department for International Trade, set up by Theresa May to put some flesh on the bones of her slogan, has prioritised arms sales for Britain’s post-Brexit industrial policy.

The DIT, which licences Britain’s exports guns, planes and bombs, has overseen a sharp spike in sales to repressive regimes, many of which it has identified as “priority markets”. The biggest of these is Saudi Arabia, which is using our arms to bomb into famine its political enemies in Yemen.

Our biggest 'priority market' is Saudi Arabia, which is using our arms to bomb into famine its political enemies in Yemen

Liam Fox, who runs the department, has said he will “personally lead on helping the defence and security industries to export and will be involved in the most significant global deals across all sectors”. It is remarkable that a figure like Fox remains in charge of anything, least of all Britain’s trade policy. In 2011 Fox was forced to resign as defence secretary after being accompanied on several trips to key UK arms markets by the businessman and his friend Adam Werrity, who did not work for the government and had not been security-checked.

Fox likes to tell us that there is moral virtue in selling arms to our allies because they save lives and improve global security. He says that Britain has one of the most robust arms export control regimes in the world. He also says that the arms industry is a huge boon for the economy, tax revenue and employment in this country. These are useful myths to defend his government’s actions.

Our arms export control regime clearly states that it is illegal for the government to licence weapons to nations that oppress their own people or violate international humanitarian law. The UN has said that Saudi Arabia is targeting civilians in Yemen. The Yemen Data Project has calculated that nearly a third of more than 15,000 air raids in Yemen have targeted non-military sites. By selling arms to Saudi Arabia, which uses them to bomb hospitals, schools, food storage sites, ports, hotels, centres for the blind and funerals, we violate British law.

Why are we doing this? It can’t just be for the money. The UK arms export industry is fairly small. British defence exports in 2015 took £7.7bn in turnover, which was 0.27% of our GDP, and 1.6% of our exports in the same year. In value, Britain’s arms exports are worth about the same as its exports in beverages. Experts put the direct subsidy at somewhere between £104m and £453m and the indirect subsidy – mainly defence research and development – somewhere between £483m and £576m. Not only are we arming the world’s most repressive and violent regimes but the British public is paying to grease the wheels.

The taxpayer funds a huge team of sales reps for the private arms export industry many of whose priority markets (Saudi, Turkey, Bahrain, Colombia et al) appear on the Foreign Office’s list of countries of human rights concern. More than 70% of the total number of Britain’s export promotion staff focus on arms, which constitutes only 1.5% of total exports in value. Half of Fox’s new secondees have been transferred from the private arms industry.

When buyers cannot afford our weapons, the government subsidises loans for them through export credit guarantees; UK Export Finance, which is supposed to support all British exports, says 50% of the support it provides (in the form of loans or guarantees) was given to defence exports.

‘Liam Fox believes that by exporting arms, Britain can somehow project power.’ Photograph: Christopher Thomond/The Guardian

Although tiny, the arms export industry is shockingly destructive. Yemen is just one example. UK arms sold to Libya (worth £105m from 2005 to 2009) can no longer be accounted for as the arms caches of our erstwhile ally Muammar Gaddafi are now enabling Islamist insurgencies across the Maghreb, one of the poorest areas on Earth, to terrorise millions.

After the Arab spring quickly turned to winter, the UK temporarily revoked many of its arms exports to Egypt and Bahrain. But by then, of course, it was too late for the Arab citizens being tracked with UK surveillance equipment, bundled into UK armoured vehicles and killed and tortured by a military with access to all manner of UK weaponry. The British arms sold during our military adventures in Iraq ended up in the hands of Isis militants. The collateral cost of UK arms sales is incalculable.

The last refuge for men like Fox is to declare that arms exports are a boon for the economy. This is also false. In 2013 a report in the Economics of Peace and Security Journal concluded that the “literature is moving towards a commonly accepted, if not consensus, view: military expenditure has a negative effect on economic growth”. Evidence from the US shows that equivalent public investment in almost any other industry, such as renewable energy, health care or education, creates more jobs.

So why does Fox spend up to a billion pounds of our money every year to prop up such a controversial, dangerous and dysfunctional export industry? Because he is an ideologue. He believes that by exporting arms, Britain can somehow project power. But the truth is that our arms exports serve to slow our economy and disempower us against the rising tide of extremism that our arms sales help to ferment.

Rather than subsidising killing machines, Britain should be spending our wealth on building productive export industries that contribute to global development and stability such as renewable energy, civil engineering and low-carbon technology.

As a member of the Commons committee on arms exports controls – which in its past has been poorly funded and frequently fobbed off by the government – I intend to shine a light on the wilful misinterpretation by the government of this regime. Ensuring our arms exports do not sow chaos across the world necessitates a deep change to our political culture, which only a Labour government will bring. Labour has higher aspirations for our industrial base in post-Brexit Britain than trying to make money out of war and human suffering.

• Lloyd Russell-Moyle is a Labour MP and member of the Commons committee on arms export controls