He said the citizens of Borno know that the governor is behind Boko Haram.
In a statement signed by his Special Adviser on Media, Adams Kolo, on Wednesday, December 13, 2017, Sheriff criticised Shettima for trying to malign his reputation and said the governor has more significant things to worry about.
He said, "In Maiduguri, Governor Shettima cannot walk free on the streets, while Sheriff walks freely every day. In Maiduguri, the citizens know that Shettima is the Boko Haram boss and the keeper of Chibok girls."
The allegation made by the former national chairman of People's Democratic Party (PDP) comes on the heels of Shettima's recent comments about the Federal Government's reaction to the abduction of the Chibok girls.
While speaking at a book launch in November, Shettima accused former President Goodluck Jonathan of mishandling the abduction, believing it to be a political stunt to unsettle his government.
He said, "When the Chibok girls saga started, they made the President to believe that there was no abduction; that the Chibok girls were kidnapped by the governor of Borno State, ostensibly to embarrass the Jonathan administration and he believed that line of story.
"I was in Chibok, my wife was in Chibok and there was a global outcry on the issue but Jonathan was in a world of his own, created by the clowns and also the misfits around him.
"I wasn't invited to Abuja until nearly three weeks later and even when I was invited to Abuja, I was quiet thrilled that at last I was getting the attention of my leader.
"I was asked to come along with Commissioner of Police, the Divisional Police Officer in Chibok, the Commissioner of Education, the Military Commander in Chibok and the Director of DSS in Borno.
"We were all ushered in to the Villa and sadly when the President came in, he was still in the world of make-believe. He started threatening the Principal that he should tell him where the girls were. He was shouting, 'Principal, you must tell me where those girls are, Commissioner of Police, you must tell me where the girls are.'
"He immediately ordered the arrest of the Principal, the DPO, the Commissioner of Police and the Director of SSS, that they must produce the girls.
"In this very unfortunate saga, Mohammed Dikko Abubakar, the Inspector-General of Police arrested them, took them to the police headquarters and told them he cannot hold onto them because he was a man of conscience. He let them go on self-recognition.
"I was quite taken aback because I thought the solution was going to be found to a very grave national challenge. Instead, the President was still of the mindset that those girls were not abducted."
He had also remarked that Jonathan's concession to President Muhammadu Buhari after the 2015 presidential election "saved the nation from the precipice."
In April 2014, Boko Haram invaded Government Girls Secondary School in Chibok and kidnapped 276 female students.
After several escapes and releases, 113 of the girls are still in captivity of the deadly terrorist group.
In May 2017, the sect released 82 of the girls in a deal that reportedly saw the Federal Government swap prisoners for the students.