Indonesians will be forced to cough up £27 million to Britain tomorrow, £20m of it loans used to buy weapons for brutal dictator General Suharto.
The money is the next instalment of £400m of loans "still owed" to Britain from loans to Suharto's regime to buy British exports in the 1980s and '90s.
The British government revealed in November that three-quarters of this was used to buy British arms such as Hawk aircraft and Scorpion tanks.
Campaigners are demanding the debt be cleared.
They pointed to a 2010 Liberal Democrat policy to "conduct our own audit of all existing UK government and commercial debts, ruling invalid any past lending that was recklessly given to dictators known not to be committed to spend the loans on development."
But campaigners argue that despite this, in the two years since the coalition government came into power, Britain has licensed £69m worth of weaponry for sale to Indonesia of which £56m is classified as "aircraft, helicopters, drones."
Tim Jones of Jubilee Debt Campaign - which aims to clear foreign debt - said: "The Indonesian people should not be paying odious debts which come from horrendous past loans by the British government for arms sales.
"The debt should be audited and cancelled, and the UK government must stop backing loans for arms sales."
Indonesia's total foreign-owed debt is almost £60 billion. It currently pays £5.6bn a year in debt payments, around 7 per cent of government revenue.
The World Bank estimates that almost half of Indonesia's 112 million people live on less than £1.25 a day.
Indonesian human rights organisation Tapol co-ordinator Paul Barber said: "The Indonesian people are still paying in more ways than one for the repression inflicted on them in the past.
"The debts should be written off and the money used instead for a reparations programme for the victims. There should be an immediate ban on the sale of any equipment that may be used for internal repression."