LONDON, England (CNN) -- British political leader Sir Menzies Campbell has quit, blaming Prime Minister Gordon Brown's decision not to hold a snap general election.
Menzies Campbell, pictured addressing last month's annual Liberal Democrat conference.
Campbell's surprise resignation as the leader of the Liberal Democrats, the UK's third biggest political party, came after its recent poor showing in opinion polls.
There had also been speculation among some party members that, at 66, he was too old for the job compared to political rivals like 41-year-old Conservative leader David Cameron.
In his resignation letter, Campbell said that one of his aims as leader had been to prepare for a general election.
"It has become clear that following the prime minister's decision not to hold an election, questions about leadership are getting in the way of further progress by the party," he said.
"Accordingly I now submit my resignation as leader with immediate effect."
Earlier this month Brown said there would be no election until 2009 at the earliest -- by which time Campbell would be approaching 70.
An MP for 20 years and opponent of the Iraq War in 2003, Campbell was elected leader of the party in March 2006, after the resignation of previous leader Charles Kennedy.
A barrister and former sprint athlete, Campbell represented Great Britain at the 1964 Tokyo Olympics and also attended Stanford University, California.
In a statement, Brown said: "Sir Menzies Campbell is a man of great stature and integrity who has served his party and country with distinction.
"His contribution on foreign policy and international affairs is valued throughout the world. I'm sure he will continue to make a major contribution to public life."
Cameron added: "Sir Menzies Campbell has had a distinguished parliamentary career and is a fine public servant."
Campbell's departure leaves Vincent Cable, his deputy, in temporary charge of the party.
The schedule for the election of a new leader will be announced tomorrow, party President Simon Hughes said.
The last leader of the Liberal Democrats -- or its predecessor, the Liberal Party -- to hold prime ministerial office was David Lloyd George, who led a coalition government from 1916 to 1922. E-mail to a friend 
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