The government has indicated it will abandon its pledge to make it illegal for United Kingdom to go to war without MPs being given a vote.
Tony Blair's decision in 2003 to ask parliament to approve his decision to join the invasion of Iraq created the convention that MPs be given a say over use use of force. The convention also forced David Cameron to ask MPs to vote on whether or not to support his call for military action against Syria earlier this year - a vote he unexpectedly lost.
However the power to deploy the military still rests in the hands of the prime minister and there is no legal requirement for him or her to ask parliament for permission.
In March 2011, as MPs debate the deployment of British forces over Libya, William Hague told the Commons the government intended to change this ancient power: "We will also enshrine in law for the future the necessity of consulting Parliament on military action."
However appearing before the Commons constitution committee today, Lib Dem Cabinet Office minister Lord Wallace of Saltaire indicated the government had changed its mind.
He told the committee that ministers had become "increasingly nervous" that making the convention a law would leave the government open to challenges in the courts over whether its decision to engage in conflict were legal.
"Whether we should legislate on it is a large question," he said. "Legislation and judicial review go together and the government has become much more sensitive about judicial review of military action."
Lord Wallace said while the government was happy to obey the convention that parliament be asked for its consent it was "very hesitant" about going any further. "Once one gets the legal dimension into it, it might be entering an area of morass rather than of certainty," he said.
"The government has an evolving position on this," he revealed. "It is a great deal more complex than one thought, the definition of armed conflict and deployment of armed forces has all sorts of ragged edges."
Critics of the idea of giving parliament the legal authority to approve or veto military action worry that it would lead to delays in deployment that could prove militarily costly and damage the effectiveness of the missions. However advocates of the move say too much power rests in the hands of the prime minister and decisions about war and peace should be made by parliament.