Could you tell me please if it's permissible to wear the Sari (Indian dress) at home of course in front of husband or in front of Muslim women providing that the belly is covered, ex as the Muslim Indian women wear it covering all part of the body (once again not to go out, as it is not Hijaab).

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

If the wife is in seclusion with her husband, she can be in any condition [wear any clothes] she likes. The Prophet said: "Cover your 'Awrah (parts of the body that must be covered in Islam) except from your wife or whom your right hand possesses." [Abu Daawood]

As regards when she is with other women, it is permissible for her to wear what covers the 'Awrah, but it is more appropriate for her to wear descent clothes in front of them.

However, in the presence of non-Muslim women, a Muslim woman is not permitted to show anything except her face and her hands, and what usually appears [from her] when she is doing housework.

Allaah Knows best.