The startling fact came to the fore when details of those who skipped the examinations were analysed by the education department, Mr Sharma, who also holds the education portfolio, told PTI in an interview.
The state board exams were in the news earlier this year as a large number of students did not turn up due to "strictness" and effective use of a special task force and local intelligence by the government to keep a tab on the cheating mafia.
"We have come to know that about 75 per cent of those who skipped the examinations were from neighbouring states. Also candidates from countries like Nepal, Bangladesh, Saudi Arabia and the UAE were among them," Mr Sharma said.
He said the state government took the help of the Special Task Force (STF) and local intelligence to curb the activities of the copying mafia with an aim to "continue with our motto of ensuring sanctity of the examinations".
"The copying mafia used to take contracts guaranteeing success in class 10 and 12 state board examinations. Impersonators were made to appear in the examination in place of real candidates and centres were earmarked where copying could be facilitated easily," he said.
The government had also decided, Mr Sharma said, to install CCTV cameras at all examination centres to keep a hawk-eye vigil on the activities going on there.
"However, installation of cameras in over 10,000 schools would have cost over Rs 400 crore and the state did not have that budget. So, we decided that only schools having CCTV cameras, boundary walls and other relevant facilities will be used as exam centres," he said.
"I personally monitored the examinations and as soon as I got any input, I shared it with the STF and immediate action was taken," he said.
"Those impersonating others or involved in replacing answer sheets before they reached evaluation centres were not able to do so due to these effective measures," said Mr Sharma.
The UP board examination for class 10 and class 12 were held between February 6 and March 12. About 66.37 lakh students registered themselves for this year's exam - 36.55 lakh for Class 10 and 29.81 lakh for Class 12.
In 2017, the overall pass percentage for class 10 was 81.18 and for Class 12 it was 82.62.
The deputy chief minister said this year's results of both the classes will be declared by the end of this month.
"We will be uploading the copies of toppers online so that students can see and follow them during their preparations," he said.
About next year's exams, he said Aaadhar card will be made compulsory for class 9 and class 11 students filling forms for the board examinations. It will help identify them and further check the menace of copying, he said.