It’s happened at last. Liam Fox, one of the most gung-ho militarists ever to occupy the post of Defence Secretary, has returned to the backbenches. All the excuses and half-truths his supporters could come up with have not saved him. But his departure will be largely pointless if we don’t learn a great deal from the Werrity scandal. When it comes to dodgy practices involving arms lobbyists and the Ministry of Defence, Adam Werrity is only the tip of the iceberg.

Adam Werrity appears to have lobbied Fox on behalf of arms-related companies without civil servants present. Whether the presence of civil servants would have made any difference is open to debate. The MoD’s tendency to lobby for the interests of arms dealers is now widely recognised. Labour’s shadow trade minister Wilf Stevenson (a member of the House of Lords) referred to it only last month, describing the situation as “bonkers”.

There is a revolving door between government and the arms trade, allowing a string of former ministers, civil servants and generals to retire to lucrative roles on the boards of arms companies. In 2006, multinational arms company BAE Systems used its influence on Tony Blair to ensure that they were effectively placed above the law, as Blair pressured the Serious Fraud Office into dropping a criminal investigation into BAE’s Saudi deals. Former Foreign Secretary Robin Cook wrote in his memoirs that the head of BAE had “the key to the garden door at Number Ten”.

On Sunday, it will be five years since I joined hundreds of other campaigners to surround the central London offices of the Defence Export Services Organisation (DESO), a unit of the MoD that promoted private arms companies. In a blatant example of a conflict of interest, DESO’s boss received both a civil service salary and a “top-up” payment from the arms industry.

DESO’s closure was announced by Gordon Brown’s government in 2007, following a long-running campaign by the Campaign Against Arms Trade (CAAT), the Fellowship of Reconciliation and other groups. The arms industry reacted with fury. They lobbied to ensure that DESO’s replacement was only slightly weaker. DESO’s functions were transferred to UK Trade and Investment (UKTI), a unit of the Department for Business that promotes British exports. UKTI now employs more staff in its arms section than in all civil sections combined – even though arms make up only 1.5% of UK exports.

This resignation is not enough. We need an end to the sort of practices demonstrated by Liam Fox and Adam Werrity. We need a thoroughgoing, genuinely independent inquiry, not only into the MoD but into all government relations with the arms industry.

This is about power. It is widely understood that arms dealers are helping to suppress human rights around the world with their supply of weapons. It is vital to realise that they are also undermining democracy in Britain with their excessive and corrupting influence at the heart of government.