Mumbai, Jan 5 (PTI) Tabu, who is sharing screen space with Katrina Kaif for the first time in their upcoming film "Fitoor", says the "Phantom" star is the most hardworking actress she has ever worked with.

"Katrina is the most hard working actress I have ever met, seen and worked with. I had three days to prepare... the involvement with which she works is amazing," Tabu told reporters here at the trailer launch of "Fitoor" last evening.

Director Abhishek Kapoor too thinks Katrina is completely into her work.

"I think Katrina has Fitoor (a kind of madness for something) of work.... the way she works is amazing. She is very dedicated towards her work," Abhishek said.

Katrina says she enjoyed shooting with Tabu, who plays her mother in "Fitoor".

"The hardest film acting that I had to do is to pretend that Tabu is my mother. She doesn't look like my mother from any angle. She is like a friend. I can't call her mother," the 32-year-old actress said.

"Earlier, I had not interacted much with her but while we were working on this film I discovered she is so warm and a down to earth person. When you are acting in front of a great actor you should not get lost in their performance... you have to contribute. It was gracious enough of her to come on board."

"Fitoor" is a modern-day take on Charles Dickens' 1861 novel "Great Expectations".

The makers had originally zeroed in on Rekha to essay the role of Begum which is inspired by Miss Havisham. Now Tabu is playing this role. Earlier in "Haider" too, Tabu had played the role of a complex mother.

"I had two days to get into the skin of the character. I don't know what the process was like. I just went into it initially with confused head as we were shooting the last scene first... I was trusting my director as I known him since a long time," Tabu said.

"Fortunately or unfortunately they (makers) come to me with these kind of characters. So I am kind of used to portraying these characters on screen. I think it is something about me that I can play complex and difficult people."

The film is set to release on February 12.