Too little is being done to police the internet as an "emporium" for selling dangerous weapons in the UK, says a group of MPs.
Fears were raised about arms fairs
In a report on arms exports, the Commons Quadripartite Committee says the government does little or nothing proactive to police the internet.
MPs praised comedian Mark Thomas for unearthing evidence of stun batons being sold through websites in the UK.
They also said more details about exports to Israel should be revealed.
Mr Thomas told the MPs about a website run by a UK company which offered introductions to Chinese and Korean arms manufacturers advertising stun batons through another website in Britain.
And in November 2004 a website of another UK firm offered stun batons and stun guns for sale, he said.
But when the MPs asked Trade Minister Malcolm Wicks about the issue, he said there was no official at the Export Control organisation dedicated to reviewing the internet for any rules being broken.
He said all available evidence was used when concerns about companies were raised.
The MPs were not reassured, and said: "The government's response to the challenge of the internet as an arms emporium is too passive and fails to take account of the role it now plays in promoting and facilitating commerce and exports across the world."
Mr Thomas also gave the committee evidence about companies at last year's Defence Systems and Equipment International (DSEI) fair in London offering to sell electro-shock weapons, leg irons and stun weapons.
Mr Wicks said he was "distressed" by the findings and the authorities had quickly shut down the exhibition stands concerned.
But the MPs argue the authorities should do more to "actively seek out breaches of export controls at arms fairs".
"Within the defence industry, there are contractors who, either through ignorance or deliberate intent, breach the rules on strategic exports," says their report.
"The authorities need to seek out these breaches and the perpetrators."
Amid the Middle East crisis, the report also says the government needs to explain its policy towards Israel, which is not allowed weapons which could be "deployed aggressively" in Gaza and the West Bank.
It says ministers should give examples where they have refused to give export licences to Israel for certain equipment.
The committee also urges the government to examine arms export applications for Saudi Arabia more carefully because of human rights concerns.
And it says it is worried about the controls on exports of goods which can be used for both civilian and military purposes.
"With tighter controls on the export of military goods there is a risk that those who cannot obtain arms by legitimate routes will turn to dual-use items," it argues.
The committee says it is not convinced that exporters of such goods know about the risks or their obligations.
It fears the Revenue and Customs agency is not stopping exporters who inadvertently, but persistently, break the rules.
The report also presses for all arms brokers operating within the UK to be registered and regulation of UK citizens working abroad to be extended to cover those dealing in missiles with a range below 300kms.
Labour MP Roger Berry, who chairs the committee, said: "Limiting weapons proliferation from small arms to biological agents is one of the major political issues of our time.
"It is quite literally a matter of life or death. Export controls are an important part of the solution."
Mr Berry said the government had a good record in being more open about arms exports and promoting an international arms trade tray to help tackle irresponsible sales.
But there were still gaps in the controls, he said.