LONDON (Reuters) - Former cabinet minister Clare Short, a vocal critic of Prime Minister Tony Blair and the war in Iraq, has quit the Labour Party, a party official said on Friday.

Short, the former International Development Secretary, initially voted in favour of the 2003 invasion of Iraq but then resigned from the government, saying she had been misled into supporting the war.

Short sent a letter to Jacqui Smith, a Labour MP leader, on Friday announcing she was quitting the Labour grouping in parliament, a spokeswoman for Smith said.

She plans to stay on until the next election as an independent Labour MP.

Shorts decision is an embarrassment to Blair, who won three successive general elections but has pledged to step down within a year after his popularity slumped over the Iraq war and his pro-market reforms.

Labour reprimanded Short last week after she said she would not stand for another term as a Labour MP and hoped the party would lose its majority at the next election.

In her resignation letter, obtained by the BBC, Short accused Blair of using "a series of half-truths and deceits to get us to war in Iraq."

She said the Labour Partys large parliamentary majorities in recent elections had led to "an abject parliament and a concentration of power" in Blairs office that had produced "arrogant, error-prone government."

Neither Short nor any of her aides could be immediately reached for comment.

Blairs spokesman declined comment on Short.