The former deputy prime minister has angered Conservative supporters and bloggers by encouraging his followers to click their sponsored ads and take "50p out of the Tories (sic) warchest."
The Conservatives have been running an online 'Labour has failed' advertising strategy, by bidding for keywords relating to the Labour Party on Google, so links to their website appeared at the top of search results.
On Tuesday, Prescott retweeted a post from one of his followers:
"1.Google 'Labour Party' 2.Click on advert saying 'Labour have failed' 3.You've just cost Ashcroft 50p. 4.Repeat"
An hour later, Prescott with a shortened link to a Google search results page that has Conservative paid-for advertising.
Since Prescott's message was posted, it has been re-tweeted more than 30 times, resulting in , valued at around £1,000-worth of advertising.
In response, a Conservative party spokesman said: "This is just the latest in a long line of dirty tricks from the Labour Party, which stretches from Gordon Brown’s spin doctor planning smears against Conservatives. People are yearning for a change from this old style of politics."
Click fraud, the practice of encouraging others to click a rival's paid-for ads, is illegal under the Computer Misuse Act 1990.
However, Google AdWords does have a facility to detect click-fraud patterns.
Labour has distanced itself from the incident, taking the stance that what John Prescott tweets is his own business.