The internet activities of the new Tory party chairman, Grant Shapps, were under renewed scrutiny after it emerged that he secretly altered his Wikipedia biography to edit out references to his performance at school, political gaffes and the identity of donors to his private office.

The Observer has established that Shapps deleted a whole range of information from the online encyclopedia, including, curiously, a reference to his time at Watford grammar school for boys where the site had claimed he "obtained four O-levels including an A in CDT". Without revealing his identity, in contravention of the Wikipedia code of conduct, Shapps justified his edits as the removal of politically slanted or unreferenced "info" and by claiming "content must be verifiable".

However, the subjects of Wikipedia articles are "strongly encouraged" to avoid conflicts of interest by identifying themselves when they propose a change. Its code also discourages subjects of biographies to edit or add material to promote their personal interests.

A source close to Shapps said the deletion of the reference to his qualifications had been made because the O-level entry was incorrect and he had "five not four O-levels". A spokesman refused to comment on the grades he had attained.

More controversially, however, Shapps had also struck out a section on a record of donations for his private office – again anonymously. In the original entry, the Wikipedia biography said: "It was revealed in May 2008 that Grant Shapps, along with other shadow ministers, had taken large donations from companies related to his frontbench portfolio … The revelations were potentially damaging for Shapps given the extent of the donations he had received – tens of thousands of pounds from two online mortgage brokers, an estate agent, a commercial property developer and a firm of solicitors specialising in conveyancing and remortgaging – and the suggestion that these might be influencing Conservative policies."

The section referred to a letter Shapps sent to the parliamentary commissioner in 2008 admitting that industry donations were used to run the private office of the holder of his Tory housing brief, although many were said to have been recruited during the tenure of Shapps's predecessor, Michael Gove. The original Wikipedia page also said: "Grant Shapps has also received media attention for a number of unfortunate gaffes during his time on the Conservative frontbench." The Observer can disclose this section was also removed, again under the veil of anonymity, with the following explanation: "Politically slanted comments removed, repeat posting may be taken as an abuse of the system."

In its place, Shapps added a glowing testimony to his own work on homelessness. Writing in the third person, he added: "His work became sufficiently influential within the homelessness sector when he launched the Homelessness Foundation with Conservative leader David Cameron in May 2008 and leading lights from the sector all joined the advisory panel of the Homelessness Foundation."

Jack Dromey, the shadow housing minister, said Shapps gave "hubris a bad name", adding: "Grant Shapps can't hide from his past. Both he and the Conservative party were too close to Tory developers lavishing support on them."

Shapps replaced Baroness (Sayeeda) Warsi as Tory party chairman last week in the governmental reshuffle. He has been dubbed the minister for the Today programme due to the frequency of his appearances on the Radio 4 flagship news show. And according to Tory insiders, Shapps had lobbied hard for a more prominent role in the government, making some enemies within the party.

However David Cameron is said to regard Shapps as a good communicator, albeit one who is no stranger to controversy.

On Saturday, it was reported that Google had blacklisted a network of websites run by Shapps's family for breaching its rules on copyright infringement, a claim denied by a spokesman for the Tory chairman.

He raised eyebrows when it emerged he had set up his web sales business HowToCorp in 2005 under a pseudonym, Michael Green, in which he cast himself as an internet marketing guru. In 2007, under the identity of Green, he claimed audiences could "make $20,000 in 20 days guaranteed or your money back" – if they spent $200 buying his bespoke software. He previously said he had used the name Michael Green to keep the business separate from his political work.

A Conservative party spokesperson said: "Individuals are 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."