For sale of leasehold interest in property consent of lessor is necessary 

As the land is held on perpetual lease, it has to be verified if the lease deed permits transfer of lease to third parties. If it is so, your father may very well sell the entire property to any third party.

- Since, this land was taken by your father on lease , then without getting the consent or free hold the property , your father cannot sell the said land .

- Further, a lease land cannot be registered in the name of purchaser. 

- He should contact to get the land freehold from the lessor as mentioned in the lease deed. 

A perpetual lease is an agreement where the land is allotted to a person over state land in accordance with the provision laid down under the Urban Land Ceiling & Regulation Act,1976. ... Perpetual leases are always issued for some defining purpose laid down under the Urban Land (Ceiling & Regulation ) Act 1976.

It is well settled that even a permanent lease is only a transfer of the right of possession. The right of ownership or any interest therein is not transferred in such a case.

As per Allahabad high court judgment in 

Shanker Lal And Anr. vs Narendra Bahadur Tandon on 17 February, 1966, 

A lease of immoveable property is a transfer of a right to enjoy such property, made for a certain time, express or implied, or in perpetuity, in consideration of a price paid or promised, or of money, a share of crops, service or any other thing of value, to be rendered periodically, or on specified occasions to the transferor by the transferee, who accepts the transfer on such terms

While the lessor grants a lease of this property, he transfers an interest in that property to the lessee and not the property itself. It is well settled that even a permanent lease is only a transfer of the right of possession. The right of ownership or any interest therein is not transferred in such a case.

 In view of above, the lessee do not have rights to sell the property that he had taken on lease without title to the property that he has taken it out on lease. 

Your father must have got a deed of assignment for assignment of the leasehold land to him 

So your father would step into the shoes of the original lessee 

Your father is the owner of the structure which he built on the leasehold land 

Your father can assign his leasehold rights as well as sell the structure under a deed of assignment subject to any restriction stated in that  behalf in the parent lease deed 

If he is owner of the same he can. But if it's a lease land then need to check the documents before the opinion