Lord Jenkins, leader of the Liberal Democrats in the Lords, will chair a six-person body which will report back within a year.
Its review will include the alternative-vote (AV) system, which critics insist is not full PR. The committee will be confirmed at a meeting of the joint government-Liberal Democrat Cabinet committee on the constitution chaired by the Prime Minister in Downing Street.
The commission was promised in the Government's election manifesto, but a referendum would be held before changing the voting system for Westminster. The Tories are opposed to PR, and Tony Blair has said he remains to be convinced, but Labour could go into the next election committed to PR before the end of a second term of office.Reuse content