Parliament will in future be given a vote on the deployment of British troops to war, Justice Secretary Jack Straw confirmed today.

The Prime Minister of the day will be required to seek the approval of the Commons before committing forces into armed conflict abroad, he told the Commons.

A report will also have to be laid before Parliament before any such decision, setting out "the terms of the approval sought and information about the objectives and legal matters relating" to the conflict.

Exceptions will be made for "emergencies" and the need for "operational secrecy," with a requirement for MPs to be informed but not given a right of retrospective approval.

The move was among a raft of measures announced by Mr Straw to move the country towards a "new constitutional settlement" and update "how power should be exercised in a modern democracy."

Other proposals include lifting restrictions on demonstrations around Parliament and allowing Government departments to fly the Union Flag whenever they wish.

Unveiling a Government White Paper and draft Constitutional Renewal Bill, Mr Straw said government accountability was "fundamental to the health of our democracy"

Last July, the Prime Minister had announced his determination to "surrender significant executive powers" to Parliament.

After a consultation exercise, Mr Straw said sections of the Serious Organised Crime Act relating to protests outside Parliament would be repealed.

But Parliament would consider whether additional measures were needed to ensure "excessive noise" did not disrupt proceedings.

The relationship between the Attorney General and the prosecuting authorities would be "re-cast".

The Attorney will cease to have any power to give directions to prosecutors in individual cases, except in exceptional cases relating to national security.

He or she will have to make an annual report to Parliament but there would be no change in the role as chief legal adviser to the Government.

Mr Straw said the Prime Minister would be removed entirely from making judicial appointments and the Lord Chancellor from appointments below the High Court.

The ratification of treaties could not proceed without the approval of Parliament - although this did not affect current arrangements for EU and tax treaties.

He said the changes on war-making powers, if agreed, would "define a clear role for Parliament in the most critical of all decisions to face a nation - while ensuring that our nation's security is not compromised".

The Government was also reviewing remaining executive prerogative powers, like the prerogative to grant mercy.

The role of the Law Commission would be strengthened by requiring the Lord Chancellor to report annually on any outstanding recommendations from the body.

On Lords reform, he said the Government was "on track" to publish a White Paper before the summer recess.

Mr Straw said of the proposals: "They are not a final blueprint but part of the much wider programme towards a new constitutional settlement.

"They will strengthen the role of Parliament in our democracy."