Army chiefs have described as "unhelpful" a petition submitted to Downing Street in protest at plans to merge six Scottish regiments.
Scottish veterans said they would fight on, despite the decision
Save the Scottish Regiments chose St Andrew's Day for a final push.
The protest comes less than a week after the Queen gave Royal Assent for the new Royal Regiment of Scotland to be formed by March 2006.
But the Army said the petition was "particularly unhelpful" and soldiers did not need the uncertainty it caused.
The current six regiments will become five battalions of the new Royal Regiment of Scotland.
The 1st battalion of the new regiment will see the Royal Scots and The King's Own Scottish Borderers battalions merged on 1 August, 2006.
The Royal Highland Fusiliers are to become the second battalion and the Black Watch will be 3 Scots.
The Highlanders are 4 Scots and The Argyll and Sutherland Highlanders are to be the fifth battalion of the new super-regiment.
Opposition politicians joined join ex-majors and brigadiers at Westminster to hand in the petition, containing 150,000 names, calling for a change of heart.
The organisers said they would not give up, even after the merger had happened.
Colonel Tim Collins, formerly of the Royal Irish Regiment, said: "In Iraq, we have reached the milestone of 98 dead.
"That is two souls from the milestone of 100 dead and this is no time to be cutting defence.
"The cuts that are being made, be in no doubt, aren't to make anything better or fix anything that is broken, they are to produce money for the Treasury and that is not a good enough reason."
Scottish National Party leader Alex Salmond said: "Scotland's historic regiments provide the army with the best infantry soldiers in the world bar none.
Campaigners took their case to the heart of government
"The strong links that exist between the regiments and the communities they serve is one of the key reasons behind their success.
"Just as they have served the people of Scotland so well over the years, it is right for us to get behind the regiments and give them the same support. Scotland's regiments matter to their communities and to Scotland."
A statement from Army HQ 2nd Division (Scotland) said the organisers of the petition and its signatories were "perfectly entitled" to their own opinion on the future structure of the Scottish infantry.
"However, those who are serving understand that the restructured infantry preserves the best of the regimental system whilst at the same time seeking to ameliorate the less appealing aspects of the Arms Plot system such as unit moves and family instability," it went on.
Lt Colonel Niall MacGregor-Smith said it was now time to move on an appealled to the petition organisers and the people of Scotland to "get behind" serving soldiers.