Mr Odinga joined a coalition government with his rival President Mwai Kibaki to help end violence after the 2007 poll when more than 1,200 people died.
“When the ethnic drums are being sounded, we know” what that means for the country, he told the BBC.
But he said the coalition had helped bring in reforms.
In the weeks of political unrest following the December 2007 elections, some 600,000 people were also forced to flee their homes.
Four prominent Kenyans are being tried by the International Criminal Court (ICC) in The Hague for their part in organising the violence. They all deny the accusations.
Mr Odinga said his “marriage of convenience” with Mr Kibaki had produced results.
“Everyone agrees that this marriage has produced offspring… so we’ve not done badly because we’ve produced a new constitution for the country and carried out substantial reforms,” he told the BBC’s Network Africa programme.
“We’ve carried out quite a bit of reforms aimed at levelling the playing field,” the Orange Democratic Movement (ODM) leader added.
“Unfortunately we still have some politicians who believe in the past and we have seen over the last few months incitement of the public along ethnic lines… trying to balkanise the country along ethnic lines.”
He named two groups in particular – the Gikuyu, Embu, and Meru Association (Gema) and Kamatusa, a group representing pastoralist communities.
The prime minister, who has announced his intention to run for president next year, said the public needed to be aware of these “prophets of doom”.
On Wednesday, a close ally of Mr Odinga’s, Deputy Prime Minister Musalia Mudavadi resigned from the ODM, declaring himself a candidate for the presidential election.
Mr Mudavadi will now represent the recently formed United Democratic Forum, but said he wanted to represent a party that was not associated with a particular region.
A former ally of Mr Odinga, ex-Education Minister William Ruto, is also vying for the presidency – and is one those facing prosecution at the ICC over the post-election violence.
Uhuru Kenyatta, an ally of President Kibaki and son of Kenya’s founding leader, is also accused by prosecutors at The Hague of crimes against humanity, including murder and persecution.
He has said he too will be standing for president in the forthcoming elections.
The date has yet to be announced by the Independent Electoral Boundaries Commission, a new body set up as part of the coalition government’s reforms.
It is thought the polls will be in the first few months of 2013, not in December as is traditional in Kenya, which means that Mr Kibaki remain in power beyond the end of his mandate in January 2013.
Politicians may find that ethnic politics is no longer palatable to voters in Kenya where 35 year olds make up the majority of the electorate, the prime minister noted.
“The youth have no time for ethnic politics… working together with our youth, we’ll be able to change our society.”
In the interview with the BBC during a visit to London, Mr Odinga also discussed his relationship with the president and Party of National Unity (PNU) leader, who is serving his second and final term in office, saying it was “initially stormy” because of the fears and suspicion following the 2007 election.
“But thereafter we’ve set up a very good working relationship,” he said of his old rival.
“Most of the time when he’s not under the influence of the extremists on his side, I’ve found him to be a real gentleman.”
The power-sharing deal between the PNU and ODM to end the 2007-8 violence was brokered by former UN chief Kofi Annan.
The agreement had initially said that those accused of being the main perpetrators would stand trial in Kenya, but politicians were unable to agree on setting up a local tribunal; who to prosecute and how to proceed.
This is why the ICC started its investigations.