The US army doubled its use of "moral waivers" for enlisted soldiers last year to cope with the stress of the Iraq war, allowing convicted sex offenders, people convicted of making terrorist threats and child abusers into the military, according to new records released today.

The army gave out 511 moral waivers to soldiers with felony convictions last year, relaxing its recruiting standards in order to admit them. Criminals got 249 army waivers in 2006, a sign that the high demand for US forces in Iraq has forced a sharp increase in the number of criminals allowed on the battlefield.

The felons accepted into the army and marines included 87 soldiers convicted of assault or maiming, 130 convicted of non-marijuana drug offences, seven convicted of making terrorist threats, and two convicted of indecent behaviour with a child. Waivers were also granted to 500 burglars and thieves, 19 arsonists and 9 sex offenders.

The new data was released by the oversight committee of the House of Representatives, which also noted that "poor record-keeping and maintenance" prevented the military from tracking how many convicted criminals had received moral waivers before 2006.

Henry Waxman, the Democratic chairman of the oversight panel, wrote to Pentagon personnel chief David Chu to seek more details on how directly the rise in waivers stems from Iraq-related recruiting needs.

Waxman told Chu that while "providing opportunities to individuals who have served their sentences and rehabilitated themselves" is important, the waivers are a sign that the US military is stretched too thin.

The total number of moral waivers in the military reached 34,476 in 2006, or nearly 20% of all enlisted soldiers, according to the Palm centre at the University of California.

Recruits with felony convictions are more likely than other soldiers to drop out or be released from the military, often at a significant cost to the US government.

More than one felony conviction disqualifies recruits from the army or marines, even with a moral waiver, but the navy and air force can admit those with multiple offences. Still, the army and marines have stepped up their moral waivers while the navy and air force have cut down since the Iraq war began.