President Kibaki wants Kenyans to approve a new constitution, while Moi is leading the "no" campaign. But the body set up to enhance national integration said the personal row was undermining its efforts.

The body was set up after deadly violence following the 2007 election.

Some fear Kenya could see a repeat of the post-election clashes in 2007 and 2008, which left some 1,300 people dead and 300,000 homeless.

According to the BBC, Moi, who led Kenya for 24 years, said on Wednesday that Kibaki should not criticize him for opposing the draft constitution, as he had broken his promise to change the constitution within 100 days of being elected in 2002.

He also rejected suggestions he should take a rest and said he had the right to take part in the campaign like any other Kenyan.

"When I see things going wrong I will speak out."

President Kibaki, 79, had earlier said Moi, 86, was embarrassing himself during the campaign.

National Cohesion and Integration Commission (NCIC) chairman Mzalendo Kibunjia called on Moi to respect the presidency, and also urged both statesmen to refrain from statements that could bring tension to the referendum campaigns.

The referendum vote is to be held on 4 August.