Anti war activists will hold a "naming the dead" ceremony as part of their campaign to bring British troops home from Afghanistan.
MPs will join the event in central London, after which members of military families will deliver a letter to the Prime Minister calling on him to bring the troops home by Christmas. It is signed by 19 members of families who have or have had loved ones in Afghanistan.
The event comes on the 11th anniversary of the start of the war in Afghanistan.
The family members will be joined by Labour MP Paul Flynn, who was suspended from Parliament over comments he made about the conflict.
He said: "We are fighting an unwinnable war of occupation and the sooner we follow our former coalition partners in withdrawing from the country the better. Unfortunately successive governments have failed to realise this and continue putting the lives of our soldiers at risk, repeating the tired mantra that they are reducing the threat of terrorism in the UK in doing so."
About 500 British troops are due to return home by the end of this year, leaving a further 9,000 to return by the end of 2014.
The number of members of UK forces to have died since operations began in October 2001 now stands at 433, and the US toll has now hit 2,000.