Under Labour's plans to end hereditary peers' voting rights in the Lords, peers would be appointed from the different parties that make up the House of Commons "but appointed pro-rata to the way the nation voted", Mr Cook said.
His remarks on BBC Radio 4 came as Tory fury over Labour's plans for constitutional reform spilled over into allegations that a Labour government would try to steamroller proposals for a Scottish Parliament through the Commons.
John Major opened the first set-piece debate against Tony Blair in months by attacking Labour's plans as "flawed" and warned that they would become a key issue on which he would fight the forthcoming general election.
There were Tory shouts of "disgraceful" when Mr Blair refused to guarantee that legislation for the Scottish parliament would be taken entirely on the floor of the Commons, which could help to side-step possible Labour backbench rebellions.
The Labour leader accused the Tories of "dirty tricks" as his keynote speech defending the party's constitutional reforms for a Scottish parliament with tax raising powers, a Welsh assembly and reform to the House of Lords, was repeatedly interrupted.
"It's all they have got left - a few dirty tricks and that is about it," said Mr Blair. "Just look at them - have you ever seen a party more obviously preparing for opposition than that?" He said: "We support devolution - we oppose separatism. No change is the enemy of the union, not devolution. To say you support the status quo is to defy wit, instinct and history.
The only weapon that Mr Major had, Mr Blair added, was fear, but he said: "The Conservatives no longer frighten because they are no longer believed. They are not believed about this, and they are not believed about what is happening around the country as that fear is being driven out by the hope of change."
Mr Blair was repeatedly challenged over the "West Lothian question" - named after the former constituency of the Labour MP Tam Dalyell, who opposed Labour's plans for Scottish devolution in the Seventies on the grounds that Scottish MPs could vote on issues such as taxation in Westminster but Westminster MPs would have no votes in a Scottish Parliament.
He responded by quoting the 1974 Conservative manifesto proposing a Scottish Parliament, backed by Margaret Thatcher and a string of current Cabinet ministers, including Malcolm Rifkind, the Foreign Secretary; Ian Lang, the President of the Board of Trade; and Michael Forsyth, the Scottish Secretary.
Opening the debate, Mr Major rejected Labour's plans as a "ragbag", which could lead to employees in England being charged an extra 3p in the pound if they worked for companies such as Kwik Fit which had its head office in Scotland, and may be subject to the higher tax levied by Labour's proposed Scottish Parliament.
"The plans drawn up by the Labour Party - with the Liberal Democrats in tow - are a blueprint that would undermine the unity of the UK and erode the authority of this Parliament," Mr Major said.
Liberal Democrat leader, Paddy Ashdown said: "I believe this is the right moment for our country to replace some of the workings of our constitution and our political system."
David Trimble, the Ulster Unionist Party leader, said Mr Major claimed the peace process in Ulster was aimed at retaining Northern Ireland within the UK but "nobody in Northern Ireland believes him".
Sir Patrick Cormack (Con Staffordshire S) said he hoped Mr Blair would honour his pledge to Tony Newton, the Leader of the House, to allow the House to decide whether the Scottish devolution bill would be taken on the floor of the House, if Labour won the election. He condemned the plans as "ill-thought out".
Nicholas Winterton (Con Macclesfield) said devolution was "inevitably going to create tremendous conflict within the UK."
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