Wed, 11 Nov 2009 22:23 EST
Lance Corporal Joe Glenton led a protest in London last month against the continued presence of British troops in Afghanistan.
He was already facing a court martial but according to the Stop the War Coalition the new charges carry a maximum of 10 years imprisonment.
The group's convener Lindsey German said last night : 'This is not about breach of military regulations. In the last few days a range of military personnel have been speaking in the media in defence of this appalling war. I doubt if any of them have been arrested.
'This is about the persecution of a soldier who believes in telling the truth in accordance with his conscience.
'He is saying what the majority of the population believes - that this war is unwinnable and immoral. The anti-war movement will be doing everything possible to get him released.'
Lance Corporal Glenton, 27, from the Royal Logistic Corps, addressed a rally of more than 5,000 anti-war protesters packed into London's Trafalgar Square in October.
He told the crowd he had witnessed sights during his time in Afghanistan that forced him to question the morality of his role.
The married soldier, from Norwich, told onlookers: 'I'm here today to make a stand beside you because I believe great wrongs have been perpetrated in Afghanistan.
'I cannot, in good conscience, be part of them. I'm bound by law and moral duty to try and stop them.
'I'm a soldier and I belong to the profession of arms. I expected to go to war but I also expected that the need to defend this country's interests would be legal and justifiable. I don't think this is too much to ask.
'It's now apparent that the conflict is neither of these and that's why I must make this stand.'
The Ministry of Defence refused to comment when asked about the further charges.
But spokesman confirmed Lance Corporal Glenton is currently subject to disciplinary action. He said: 'I can confirm that disciplinary action against a serving soldier from the Royal Logistic Corps is currently in progress.
'As this matter is subject to court martial proceedings, it would be inappropriate to comment further at this stage.'
The soldier, based in Abingdon, Oxfordshire, is facing a court martial, adjourned to January, for alleged desertion after going absent without leave in 2007.
He is charged with disobeying a lawful command. He joined the Army in 2004.
If convicted, he faces two years in prison.
Speaking during last month's rally, he said: 'The occupation in Afghanistan is at best dubious in terms of legality and morality.
'I can't be involved in it on that basis and, not only that, I am also bound to try and stop it, try and change things.
'That's the law, the occupation of a country like that, regime change, these things are all illegal.'
He said military personnel told him not to appear at the rally.
But despite the threat of prison, he said he was determined to speak out.
He said: 'People keep telling me I'm brave but I don't feel brave at all - I feel fairly terrified. It's not going to stop me, I'm going to keep going.
'I won't be silenced. I'll keep talking and doing what I think is right.
'I have to or I'll have to live with this forever if I don't.'