The Tories have admitted a member of staff altered a Wikipedia entry on the artist Titian after a row between Gordon Brown and David Cameron.
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 Tory HQ moved Titian's birth date forward by four years.
The party admitted an "over-eager" member of staff had been responsible.
Wikipedia is an online encyclopaedia founded in 2001 and based on wikis - open source software which lets anyone alter an entry.
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."
He was speaking in the context of people learning how to deal with the current economic crisis.
'Incorrect entry'
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 emailed the BBC taking issue with this claim, saying there was no certainty about the age at which Titian died. BBC 2'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.
