Step 1: Understand the claim in the question.
We must find the leader who said the Indian Constitution was just a copy of the Government of India Act of $1935$.
Step 2: Why such a criticism arose.
Many features of our Constitution, like the federal setup, provincial administration, and emergency provisions, were borrowed from the $1935$ Act. So some members felt it was not fully original.
Step 3: Recall the critics in the Constituent Assembly.
Several members debated the sources of the Constitution. Among them, one member strongly voiced this exact complaint about the $1935$ Act.
Step 4: Identify that member.
It was Maulana Hasrat Mohani who argued that the Constitution was merely a copy of the $1935$ Act.
Step 5: Rule out the others.
The other names listed are not the ones linked with this particular and well known criticism, so they are set aside.
Step 6: State the answer.
The correct person is Maulana Hasrat Mohani.
\[ \boxed{\text{Moulana Hasrath Mohani}} \]