More details emerge of changes to online encyclopaedia made from computers in Tory chairman's office

Further details have emerged of how the constituency office of the new Conservative chairman Grant Shapps altered his Wikipedia biography to remove references to embarrassing political gaffes, the marketing website he founded and his personal fortune.

Using a series of anonymous accounts which can be traced to the Tory chairman's computers, references were deleted about his role in a 2007 byelection in west London where he impersonated Liberal Democrats online in an attempt to discredit his rivals – but forgot that he had logged on as himself.

The campaign was notable as Shapps was then a vice-chair of the Tory party responsible for campaigning. The Tory candidate came third when many felt he was favourite to win. However, the episode was airbrushed away on the online encyclopaedia.

In another series of changes after the 2010 election, Shapps's entry removed references to the company HowToCorp, which the Guardian has exposed for breaching Google's code of conduct, and to his online pseudonym Michael Green – with a comment posted that this mention of his "alter ego" was linked to a diary item that was an "unreliable source".

Gone too were links to sites which revealed the Welwyn Hatfield MP paid back £3.79 during the expenses scandal, replaced by glowing references to a Daily Telegraph piece describing him as an "expenses saint".

The revelations come after it emerged that Shapps had changed his entry in the online encyclopedia to correct the number of O-levels he obtained. He had also inserted testimony to his "influential" work on homelessness.

Shapps, who took over as Tory party chairman last week, also erased a Wikipedia paragraph referring to donations to his office while he was shadow housing minister. He told the Daily Mail: "These days when I see stuff that's blatantly wrong on my Wiki page, I just shrug my shoulders. If people want to claim I'm a Jehovah's Witness, agnostic or crashed a car into a school wall – all real edits I'd previously changed – then I just leave them to it."

The changes have not gone unnoticed. In May 2010, there appears a bizarre spat with another Wiki contributor, Widefox, over claims that Shapps was a member of the Freemasons. A spokesman for Shapps said he was not a member of the group.

Wikipedia says contributors seeking to amend entries should submit a request for an edit rather than editing directly. Its code of practice says that "editing Wikipedia with a conflict of interest is strongly discouraged".

Contributors to Wikipedia, which is run by volunteers, have noticed that Shapps appears to be editing his own entries. One administrator named Earle warns Shapps says that if he continues to "create a conflict of interest situation, administrative sanctions may result".

A volunteer media contact for Wikipedia said he could not comment on this case but "in general, if someone is really pushing it, they might end up blocked from editing".

Sources close to Shapps emphasised that the four usernames – 217.155.38.72, 90.196.154.2, Historyset and Hackneymarsh – could only be linked to "computers in the constituency office of the Tory chairman".

A Conservative party spokesman said: "Contributors to Wikipedia are encouraged to remove immediately any contentious material about a living person that is unsourced or poorly sourced.

"Individuals are also free to monitor the information that is available about them online – particularly when this information is purposefully vandalised by others.

"This is absolutely not in breach of Wikipedia rules – and it is completely false to suggest that Wikipedia have contacted Grant in this regard."

Labour MP Steve McCabe MP told the Guardian that the Tory chairman "seems to have more imaginary personalities than Walter Mitty".

"This latest imbroglio is reducing the current Tory Party Chairman to a farcical figure. No wonder the Tory-led Government can't start to deal with the myriad problems from a recession made in Downing Street to the debacle of the GCSE results with Grant Shapps overseeing proceedings."

Note: This article was amended on Wednesday 12 September morning to add reaction from a Labour MP.