MPs will today hold a three-hour emergency debate on the government's deployment of 1,700 royal marines to Afghanistan.

The Commons speaker, Michael Martin, yesterday agreed to Conservative demands for the debate after they expressed anger at the lack of consultation over the "very major escalation" in the UK's military commitment to the country.

The call came as defence secretary, Geoff Hoon, admitted that the combat commitment was "open-ended" and could involve more troops.

MPs fear that the commandos could now be sucked into a dangerous and open-ended war.

In a separate move, an MoD briefing note passed to today's Telegraph reveals that the government is secretly planning to reduce the size of the UK's armed forces.