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Police investigating the disappearance of Madeleine McCann in Portugal have been told how their prime suspect, the Briton Robert Murat, was impatient to rent a car two days before he was first questioned by police, because he claimed his own was needed by those involved in the search for the four-year-old.

Staff at the Autorent 3 dealership here say they asked Mr Murat to wait until after their lunchbreak finished at 3pm last Saturday - Madeleine's fourth birthday. But he said he needed the vehicle immediately.

Maria Rocco, the member of staff who received Mr Murat's call at the dealership, opposite the church where Madeleine's parents have been praying regularly, called police to report Mr Murat's request after hearing of his arrest. "He said: 'I need a car for myself because the English people who are looking for the little girl need to borrow my car," Mrs Rocco recalled. "You could tell from his voice that he needed it in a hurry. I was puzzled. Why would he need to lend his car to somebody else [in the search]?"

The revelation comes after police questioned Mr Murat's mother, Jennifer, yesterday about her son's alleged involvement in Madeleine's abduction. Yesterday it was reported that police arrived at Mrs Murat's £600,000 villa in Praia da Luz to quiz her about her role as her son's alibi on the night of the abduction.

Results of these interviews will join Mrs Rocco's evidence, which was supported by the form Mr Murat signed when he collected a Hyundai Jetz at 5.16pm that day. It will certainly have interested Portuguese police since the ground search for Madeleine was being scaled down last Saturday and Mr Murat's mother's car, a green VW van, seen in the area that weekend, was available. Mr Murat has indicated that he was aware last weekend that police were tailing him and that he complained to them about this shortly before the raid on his house.

Police are also focussing their inquiries on telephone calls between Mr Murat and a Russian computer scientist, Sergey Malinka. One of these was reportedly made by Mr Malinka a few minutes after 10pm on 3 May - the time when Madeleine's parents discovered she was missing from her room at a Mark Warner resort in the Algarve town.

The Russian left his flat in Praia da Luz on Wednesday night with police who had removed a laptop and two computer hard drives. Mr Malinka declined to discuss his phone calls with Mr Murat yesterday, but insisted that videos seized from his house had no paedophile content. He confirmed his name and number were in Mr Murat's phone.

Yesterday, Mr Malinka protested his innocence. He said: "I am not a suspect in this case. I am merely a witness questioned like eight or nine others. Everything that has been said about me is lies... There have been claims in the press that I am some kind of sexual maniac or paedophile. It is nonsense. My career is destroyed and my life is ruined."

Mr Malinka remains one of the investigation's 100 witnesses, rather than a suspect like Mr Murat, but the policeman leading the inquiry, Oligario Sousa, did not rule out that situation changing. "[He is] not a suspect but it could be in the course of the investigation that something could change," he said. "It's a very dynamic investigation."

Mr Malinka, who moved to Portugal from Moscow seven years ago, says he spent several weeks helping Mr Murat and his German girlfriend, Michaela Walczuch, set up a property website a year ago. He said Mr Murat was a client, not a friend, despite reports that they had been photographed together several times after Madeleine's disappearance. "I had a working relationship with him [Robert]. How friendly can you be with a client?" he said.