1. Sir, the recruitment to the Central Govt., or any Public Office is done through a proper recruitment process based on the Recruitment Rules as laid down in respect of said Govt. or Department in respect of particular post. The Hon'ble Supreme Court has in the case of State of Karnatka -vs- Uma Devi & Others (Year 2006) decided that a public servant can be recruited only through proper procedure as laid down through Recruitment Rules as applicable.
2. Therefore, a contractual employee, even though having a long period of service on contract basis, will not attain regularisation in the Government department in which he is working on contract basis. If you are within age and eligible as prescribed for such recruitment ,you can apply to the various posts of government as advertised from time to time. With best wishes.