A committee of MPs has warned that Britain's controls on arms exports are "complicated" and failing to protect human rights.

The review of licensing decisions taken in 2002 and 2003 concluded that the vast majority were uncontentious.

But a joint report from the Commons defence, foreign affairs, international development and trade and industry committees expressed concern about government rules designed to ensure that military exports are not "misused" by those who buy them.

"For example, the government does not seem to have investigated adequately claims that equipment exported to Indonesia has been used in military operations in Aceh province in breach of assurances previously given, and possibly in violation of human rights," said the report.

The committees said they were continuing a "dialogue" with the government over its strategic export controls.

But they expressed criticism of the complexity of existing licensing procedures.

"The British export control system is complex and often misunderstood, even by industry," the report warned.

"It should impose no more burdens on British industry than necessary.

"Changes have recently been made, but other European countries seem to have simpler systems, which appear to give their industries a competitive advantage on the export market.

"The British system has been made even more complicated with the introduction of controls on trade between second and third countries and on intangible (electronic) transfers of military technology.

"We are not convinced that the new system targets as accurately as it should those activities of most proliferation concern."

The committees also called for a renewed diplomatic effort to ensure that international export control regimes work effectively.

And there was a warning that HM Customs and Excise bring "very few" prosecutions for breaches of export controls.

"It is essential that they and the intelligence and security agencies are adequately resourced if illegal proliferation is to be stemmed," said the report.

Liberal Democrat foreign affairs spokesman Sir Menzies Campbell said the conclusions amounted to "a searing attack on the way in which 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."