By Peter Griffiths
LONDON (Reuters) - British Labour leader Ed Miliband, the main challenger to Prime Minister David Cameron in 2015 elections, has suffered a sharp slide in his personal ratings and his party's lead has been cut to a thin margin, a poll found on Wednesday.
Miliband has faced criticism from inside and outside his party over his leadership style, his reform of Labour's historic links with trade unions and the tactics he used to effectively block Britain's involvement in possible strikes against Syria.
Miliband, saw his rating plunge to its lowest point since research company Ipsos MORI started recording it, with six out of 10 saying they were not satisfied with his performance.
Even among supporters of his center-left party, just over half (52 percent) said they weren't happy with him. That was Miliband's worst score among Labour voters ever recorded by Ipsos MORI.
Senior Labour figures have said the party's lead should be much wider at this stage in the election cycle, given the economy's poor performance until recently, and the poll is likely to increase pressure on Miliband's leadership.
"There has been much discussion over the perceived softness of Labour's lead and this poll shows that clearly," said Gideon Skinner, head of political research at Ipsos MORI.
Since beating his brother David to the party leadership in 2010, Miliband has failed to match Cameron's personal ratings.
Former Cabinet minister Tessa Jowell called for an end to the criticism, saying it had created a "sense of toxic disunity" in the party that governed Britain for 13 years until 2010 under Tony Blair and Gordon Brown.
The latest poll gave Labour a three point lead over the Conservatives, based on those certain to vote. Labour were down three points and the Conservatives up four since the last poll.
The survey also measured the leaders' net personal ratings - the number of people who say they are satisfied with their performance minus the number who are dissatisfied.
Miliband's stood at minus 36 percent, in line with lows recorded by former Conservative leaders Iain Duncan Smith and William Hague. Cameron's net rating stood at minus 20 percent.
Cameron was seen as a more capable leader, better in a crisis and with more personality than Miliband.
A run of upbeat economic figures helped push the economic optimism index to +23, its highest score since November 2009.
Ipsos MORI questioned 1,000 adults between September 7-9.
Miliband led a successful parliamentary revolt last month against Cameron's bid to seek approval in principle for military action in Syria over an alleged chemical attack - saying he was not opposed to force in theory but unconvinced by Cameron's case.
Critics accused him of acting out of political opportunism rather than principle.
(Editing by Andrew Osborn and Andrew Heavens)