David Hencke and Rob Evans – Britain is threatening to refuse export licences for spare parts for Hawk jets to Indonesia, after growing government concern about human rights abuses by the military in the suppression of rebels in Aceh.

Mike O' Brien, the trade minister, has warned President Megawati Soekarnoputri that the jets must not be used to suppress internal revolts. While in Indonesia, Mr O'Brien said: "We do have agreements to supply parts and also have further relationships with the armed forces, which might be damaged if we cannot reconcile this issue." He reminded the Indonesian government that the British-made jets – sold for training purposes – should not be used in any offensive that led to human rights abuses. The jets were used on the first day of the military operation last month to flush out rebels in Aceh by providing air cover for the army.

Mr O'Brien also expressed concern about the killing of three boys – aged 11, 13 and 14 – by the army in Aceh because they were believed to be terrorists. The minister has told the Indonesian government that there was no justification for killing boys as young as that.

Mr O'Brien's warning is an attempt to try and enforce Robin Cook's ethical foreign policy which promised that Britian would not export arms to regimes that used them for internal repression. The 24 jets were sold in 1996 by the Conservatives without any restriction on their use, but Indonesia voluntarily signed up to a new agreement, after Mr Cook became foreign secretary, that introduced new restrictions. Indonesia still maintains this is a "gentleman's agreement" which has no force and anyway only applied to East Timor – now an independent country after Indonesia had occupied it for decades.

The Foreign Office minister has been under pressure from Labour backbenchers – notably Jeremy Corbyn, MP for Islington North – to take a tough line with Indonesia over use of the jets. Mr O'Brien told him about his recent visit: "I reminded them of the assurances about the use of British-supplied military equipment in Aceh, and warned of the possible consequences for defence sales and defence relationships if there was a breach of the assurances.

I also stressed that Indonesian military action in Aceh should be proportionate and in accordance with international standards on human rights. "The Indonesian government confirmed that British-supplied Hawk aircraft were used in Aceh on May 19 2003, but claimed they were not used in violation of the assurances. We will be using all available sources of information to monitor the use of British-supplied equipment and will follow up all credible allegations on the misuse of British military equipment." He added: "In August 2002 the British government received advance notification from the Indonesian government that they may deploy British-built military equipment to Aceh for casualty removal and logistics. Hawk jets do not perform these tasks. Ministers agreed in September 2002 to fresh assurances that British-built military equipment would not be used to violate human rights anywhere in Indonesia nor would the equipment be used offensively."