ODM has disputed the appointment of President Uhuru Kenyatta as UNICEF's global champion for youth empowerment.
Executive director Oduor Ong'wen wrote to the UN body asking them to "revoke the decision and apologise to Kenyans".
"We urge your office to keenly review and rescind this appointment and offer an apology to the many families in Kenya."
"...families whose children were physically and sexually assaulted and the millions of young unemployed Kenyans chocking under the heavy weight of official government corruption and plunder," Ong'wen said.
Uhuru accepted the UNICEF appointment last week.
His role as the global champion will entail advocating the promotion of universal healthcare, education and nutrition.
But in a statement on Tuesday, Ong'wen said the appointment is in bad faith.
"We reject this appointment that is a travesty of an organisation that prides itself as the champion of children rights across 190 countries and territories," he said.
Ong'wen said through the appointment, UNICEF has legitimised the sexual assault on women and girls, the physical violence on all children and worst the killing of children during the last elections.
During the elections, a six-month-old infant died from a head fracture after she was reportedly clubbed by police officers who raided their home during post-election protests on August 11.
"UNICEF has legitimised government corruption and wanton looting of the public fund on programmes conjured up as youth empowerment projects," Ong'wen said.
"We are shocked at this offer and wish to register our indignation to you."
During her visit to Kenya, the United Nations Children’s Fund executive director Henrietta Fore assured the country of support in achieving universal healthcare.
Fore commended Uhuru for the "Big Four Agenda", terming it a well-thought-out plan that would project Kenya as a model in the region especially in the provision of healthcare to children.
No to appointment
But after the appointment, the UN spokesman Stephane Dujarric said he has no idea that Uhuru was appointed as a youth champion.
Speaking to the Inner City Press on January 23, Dujarric said: "...the director spoke about the need for youth to be engaged and the president said he will support that but beyond that, I am not sure of any appointment."
Kenyans on Twitter also rebuked UNICEF for appointing Uhuru as the global champion for youth empowerment.
Under #shamefulUNICEF, those opposed to the move expressed their displeasure saying global bodies need to relook at their choice of some ambassadors.
"@UN has almost always goofed on the appointment of so the called ambassadors. It was Mugabe just before his downfall and now @UKenyatta!" @Douglasorangi said.
@AmedoShair said "that UNICEF has appointed Uhuru the global champion for youth empowerment. Stinks,reminds me of the WHO appointing Mugabe."