The Orange Democratic Movement will on Sunday start grappling with challenges that have tested its unity since the beginning of the year.

The party's MPs gather in Naivasha ostensibly to strike a deal on a new Constitution and prepare for party elections to fulfil the requirements of the Political Parties Act.

Already battle lines are drawn within the ranks of the MPs in what could come down to a test of loyalty for their leader, Prime Minister Raila Odinga.

A section of MPs have been dubbed as rebels for seeking the dissolution of the Pentagon, demanding that Mr Odinga keeps off the Mau Forest evictions, appointment of a new party chief whip and establishment an Official Opposition in Parliament.

However, party secretary general Anyang Nyong'o said these issues are not part of the agenda for the meeting scheduled to start this afternoon and close on Monday.

It will be the first meeting of the party MPs and those from its affiliates.

Prof Nyong'o says the main items include aligning the party's constitution to the Political Parties Act which came into force in July and the upcoming nationwide party elections.

"Any other issue being bandied around is sheer speculation by people who are excited to get their names in the media," Prof Nyong'o said.

But Chepalungu MP Isaac Ruto says the party leadership "will not shy away from issues that would make the party lose its credibility."

Mr Ruto's sentiments are echoed by his Cherangany colleague Joshua Kutuny, who adds that the party's chief whip, Gem MP Jakoyo Midiwo has to be "disciplined for his arrogance."

Mr Midiwo has come under attack from the Rift Valley's rebel MPs over remarks he made that their rebellion was being bankrolled by a certain PNU politician.

The Gem MP had dismissed the rebel clique as a group of "selfish" politicians.

On his part, Deputy Speaker Farah Maalim says the MPs making comments were just "indisciplined" with a lame excuse of exercising democracy.

"I think we are taking democracy to the extreme...there has to be some kind of party discipline," Mr Maalim said.

Budalang'i MP Ababu Namwamba was cagey about the side-issues and insisted on toeing the party line of getting information from the secretary general, Prof Nyong'o.

Mr Namwamba, the secretary of ODM's Parliamentary group, however added that the opposition matter would also be discussed.

Divisions, discontent and cold wars have been brewing in ODM since the party teamed up with PNU to form the Grand Coalition government.

The issues blew out when the Cabinet was announced with those who were left out crying foul.

Other contentious issues that have since fuelled acrimony within the party are amnesty for youths arrested over post-election violence and conservation of the Mau Forest.