Assurances arms exports from the UK are not used to abuse human rights are effectively worthless, MPs have said.
MPs want to know what part British-made equipment has played
The joint Commons committee on defence exports said certificates, supposed to prevent the misuse of exported arms, lacked "legal or political backbone".
"We conclude that without more legal or political backbone, end-use assurances are not worth the paper they are written on," they said in a report.
The MPs highlighted the use of UK-made equipment by Indonesia.
The committee, made up of members from the defence, foreign affairs, and trade and industry committees, accused ministers of failing to investigate reports that Scorpion armoured vehicles and Hawk aircraft had been used against separatist guerrillas in the province of Aceh.
"We have seen no evidence that the government has taken any action (other
than talking to the Indonesian authorities) to investigate claims that British
built military equipment has been used in violation of human rights or
offensively in Aceh," the report said.
"There is little point in the government seeking assurances on the end use of equipment if it is not prepared to conduct a thorough investigation when
evidence emerges that those assurances may have been breached, or if it is not prepared to take punitive action when assurances have indeed been breached."
The MPs urged the government to set out what moves it had made to locate TV footage of Indonesian military action in Aceh to see if there is evidence of British equipment being utilised.
And they criticised the government for "unreasonably" denying them access to some official documents relating to arms export licence applications.
Oxfam, which campaigns for tighter controls on arms sales, welcomed the MPs' report.
Head of advocacy, Phil Bloomer, said: "Unless the government heeds their advice and takes urgent action, British-sold weapons will continue to end up in war zones where they could be
used to kill civilians."
Liberal Democrat foreign affairs spokesman Sir Menzies Campbell said the report was a "searing attack" on how government policy is implemented.
"There is no point having declarations of principle if these are not observed in practice," he said.
"If we are serious about human rights we should be rigorous in not exporting arms to those who abuse them."
Paul Barber, of the Campaign Against the Arms Trade, said the report had exposed a "lamentable lack of concern" about the use of British equipment in Indonesia.
"There are grave risks that equipment will be used against innocent civilians and we repeat our long-standing call for the Government to introduce an
immediate embargo on the supply of British military equipment to Indonesia," he said.
A Foreign Office spokesman said the government had made "unprecedented improvements" to the transparency and accountability of UK arms export controls.
But some information could not be released because it was for example commercially confidential.
As to the situation in Indonesia, he said it had proved difficult to find out what was happening in Aceh.
"We have investigated claims by NGOs (non-governmental organisations) and others of the use of military equipment in Aceh several times since last May, following the resumption of hostilities in Aceh.
So far, there has been no credible evidence of British equipment being used either offensively or to breach human rights."