A total of 900 more Armed Forces reservists are to be sent to Iraq, Defence Minister Ivor Caplin has said.
Reservists make up 25% of the UK's defence capability
The group, from the Territorial Army in Scotland, will replace 750 part-time men and women serving in and around Basra who are due home in May 2005.
The additional 150 reservists will take over a hospital currently being run by the regular army.
They will be deployed from April 2005 onwards, Mr Caplin said in a written answer in the House of Commons.
A Ministry of Defence spokesman said the deployment was part of a rotation of troops.
He said they would be deployed to the south-east multi-national area, based around Basra.
There are about 46,000 volunteer reservists in the UK who make up 25% of the Armed Forces.
The Volunteer Reserve Force consists of the Royal Naval Reserve, the Royal Marines Reserve, the Territorial Army , the Reserve Air Forces (the RAF Reserve) and the Royal Auxiliary Air Force.