Tony Blair's premiersship is broken. Sixteen months after he led the Labor Party to an unprecedented third successive general election victory, Britain's prime minister has promised to resign. He will quit 10 Downing Street next year, three years before the end of his mandate in May 2010. The British electorate will have no say in who replaces him. That decision is reserved for Labor Party members, MPs and trade unionists affiliated to the party — an electorate made up of fewer than 1 million registered voters from a total of 44.2 million. This system needs to change.

Granted, Britain's unwritten constitution of constantly evolving common law, statute and convention has never permitted direct election of prime ministers. The monarch invites the leader of the majority in the House of Commons to form a government. Winston Churchill had no popular mandate when he forced aside the arch-appeaser Neville Chamberlain in May 1940. Nor did Harold Macmillan in January 1957, when he replaced Anthony Eden after Britain's humiliation at Suez.

In the United States, "voters don't decide issues, they decide who will decide issues," wrote columnist George F. Will. In Britain, we do not even have that luxury. Labor Party and trade union members are the decisionmakers They may even render the restricted electorate redundant by picking a solitary contender, Chancellor of the Exchequer Gordon Brown, whose allies have worked assiduously to destabilize Blair.

Despite the Magna Carta's nearly 800-year-old assertion of the rights of the community against the crown, unelected changes of national leadership were, until recently, barely controversial. Constitutional doctrine defines the prime minister as merely first among equals — the leader of his Cabinet, not the head of state. It says he is made legitimate by his party's majority, not by personal attributes. The theory has worked for centuries and even thrown up gems, including Churchill, William Gladstone and Benjamin Disraeli. Why change it now?

Well, as the grandfather of British constitutional theory, Walter Bagehot, put it, "The whole history of civilization is strewn with creeds and institutions which were invaluable at first and deadly afterwards." The nature of the job has changed fundamentally. It started with Margaret Thatcher — herself deposed by party and not country — a leader who appealed beyond traditional Conservative heartlands with the ideology the world calls Thatcherism.

Blairism may be more nebulous, but there is no doubt that it exists. Blair remade his party according to his own ideals. He led Labor into government by redefining a tired organization, overwhelmingly distrusted by voters, and rendering it freshly attractive. He emphasized the change by re-branding Labor as "New Labor."

This transformation of the prime minister's role has gone beyond public relations. The former Cabinet secretary, Lord Robin Butler, believes that Blair has rewritten constitutional tradition to increase his personal power. Britain's leading scholar of government, Peter Hennessy, calls the Cabinet "by far the most supine since the Second World War." Several of Blair's former Cabinet ministers make the point unambiguously: Blair is a president in all but name. His mandate is more personal than that of any of his predecessors.

The best indication Britain is likely to get about popular attitudes toward a Brown premiership comes from opinion polls. The most recent one, conducted by the British market research agency You Gov, indicates that only 1 in 5 voters believes Brown will make a better prime minister than Blair. Most polling suggests the electorate would reject any Labor nominee. The Conservative Party under its new leader, David Cameron, has a clear lead with voters.

In recent years, it has become common for British politicians to lament declining electoral turnout. Between 1945 and 1997, participation never dropped below 70 percent and regularly exceeded 75 percent. In 2001, it fell to 59.4 percent; 2005 saw little improvement at 61 percent. A common explanation is that voters feel participation makes no difference. One way to confirm that is to deny them influence over who controls Britain's nuclear weapons.

Brown describes the private transfer of power by which he hopes to inherit the premiership as "a stable transition." George Orwell could not have invented a blander euphemism for a constitutional coup d'etat. It is appallingly undemocratic that Blair can be ditched without a general election. It makes Britain look little better than a one-party state. If the beauty of an informal constitution is that it always adapts to new circumstances, then Britain's cannot adapt fast enough. Our new prime minister should be elected, not appointed.

Tim Luckhurst is a former editor of the Scotsman in Edinburgh.