Titian - Bacchus and Ariadne
During exchanges at prime minister's questions, the Tory leader mocked Mr Brown for talking of Titian at 90, when he said in fact he had died age 86.
Shortly afterwards a Wikipedia user registered at Conservative HQ moved his date of death forward.
The party admitted an "over-eager" member of staff had been responsible.
Wikipedia is an online encyclopaedia founded in 2001 and based on wikis, which let anyone have access to a web page.
The issue of Titian was raised during prime minister's questions when David Cameron referred to comments made by Mr Brown last month at the World Economic Forum in Davos.
Mr Brown had said: "I'm reminded of the story of Titian, who's the great painter who reached the age of 90, finished the last of his nearly 100 brilliant paintings, and he said at the end of it, 'I'm finally beginning to learn how to paint,' and that is where we are."
'Brilliant'
He was speaking in the context of people learning how to deal with the current economic crisis.
In the House of Commons Mr Cameron said, to laughter from Conservative MPs: "You told us the other day you were like Titian aged 90. The fact is Titian died at 86."
Shortly afterwards several people e-mailed the BBC taking issue with this claim, saying there was no certainty about the age at which Titian died. BBC Two's Daily Politics also reported that his Wikipedia entry suggested he had lived to 91.
At 1234 GMT, shortly after PMQs ended, the page was changed by someone registered as being at the Conservative Party's HQ in London.
The artist's date of death was altered from 27 August 1576 to 27 August 1572.
A Conservative spokesman said: "This was an over-eager member of staff putting right an incorrect entry on Wikipedia."
At 1229 GMT, another user - registered as being in Sutton, Surrey - altered Titian's date of birth from c.1485 to c.1490.
This, when combined with the intervention by the Conservative HQ user's intervention, would have made his lifespan 81 or 82 years.
The page has since been changed a number of times and there has been a heated debate taking place citing different authorities' views on Titian's most likely birth and death dates.
Later, Labour MP Peter Kilfoyle asked the deputy Speaker of the House of Commons: "I wonder whether you could tell the House whether you have had representations from the leader of the opposition so that he might correct the comments that he made about Titian.
"Or is it enough in this modern age for the leader of the opposition's staff simply to alter Wikipedia?"
Following several seconds of uproar, the deputy Speaker replied: "The honourable gentleman, as an experienced member of this House, knows that is not a point of order for the chair but his comments are on record."
Titian - Tiziano Vecellio - was born in Italy and his works include Bacchus and Ariadne and Diana and Actaeon.
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