In a statement at al-Nubariya, north of Cairo, on Monday, Mubarak, the candidate for the ruling Egyptian Democratic Party, said the political move that accompanied amending Article 76 of the constitution and other amendments proved that Egypt was taking the right path.
The amendment opened the door for further political reforms and would not be the last one, Mubarak said.
But opposition parties said on Monday that Egypt's state newspapers, which dominate the printed media, were openly supporting Mubarak in the country's first presidential elections despite instructions to be neutral.
State-owned newspapers have written editorials endorsing Mubarak and the platform of his ruling National Democratic Party for the 7 September vote, critics charge.
They are also accused of making fun of some opposition parties and their ideas.
The state papers devote much of their front page space to Mubarak's campaign promises, often confining rivals to a few paragraphs at the bottom or to the inside pages.
Opposition parties complained that Al-Ahram, the most prestigious Egyptian newspaper with a history dating back to 1876, was one of the worst offenders under new editor-in-chief Osama Soraya, who was appointed on 4 July.
"In the editorials there is complete partisanship on the part of the writers in favour of President Mubarak"
Spokesman for the campaign of Wafd Party Magdi Sirhan
An independent monitoring organisation said it had received a disproportionate number of complaints about the front page of Al-Ahram, which has often given more space to Mubarak's campaign than to all the other nine candidates' campaigns put together.
Ghada Shahbandar, spokeswoman for the monitoring group Shayfeencom, said: "The main issue has been the page one coverage in Al-Ahram."
Magdi Sirhan, spokesman for the campaign of Wafd Party candidate Numan Gumaa, said: "There's clearly bias in the amount of coverage they (the state papers) give the candidates and in the language they use in their coverage.
"In the editorials there is complete partisanship on the part of the writers in favour of President Mubarak," he added.
Wail Nawara, spokesman for candidate Ayman Nur of the al-Ghad (Tomorrow) Party, said he had never expected much else from the state newspapers, adding that al-Ghad would like to convert them into truly independent entities.
Some of the parties say they have complained about coverage to the presidential electoral commission but have not received a reply.
State radio and television, under the direct control of the government, have broadly respected rules that allocate time limits to each campaign.
State newspapers are under less direct control - they are nominally owned by parliament's upper house and are governed by a Supreme Press Council dominated by the ruling party.
The press council has issued guidelines saying election coverage should be neutral, but these are open to interpretation.