Turnout was low at 14.5%; Simpson received 60,048 votes compared to the 39,307 of his nearest rival, the far left candidate Jerry Hicks.
Kevin Coyne, who spearheaded the challenge that that led to the election, received 30,603 votes.
It is believed that the vote was held to avoid a legal challenge to Simpson's plans to stand beyond the previously compulsory retirement age of 65. He will now remain in his position until December 2010.
Simpson's victory comes despite negative press surrounding his allegedly lavish lifestyle and newspaper reports of a rift with fellow general secretary Tony Woodley.
It was announced last month that Simpson was to take legal action against The Times for a series of stories written in January.
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