A former RUC man is pursuing “potentially significant” information received after the broadcast of a new TV documentary about the disappearance of Madeleine McCann, her family’s spokesman has said.

More than 50 calls were made to the McCanns’ investigative hotline following the airing of Thursday night’s programme, which highlighted three separate sightings of a suspicious man before the little girl vanished.

The callers offered “real, new information”, including details of possible sightings of the missing child, family spokesman Clarence Mitchell said.

Madeleine was nearly four when she went missing from her family’s holiday flat in Praia da Luz, southern Portugal, on May 3 2007 while her parents dined with friends nearby.

The new documentary highlighted three witnesses who saw an odd stranger who appeared to be watching the McCanns’ apartment in the days before the little girl disappeared.

An artist’s impression based on one account of the man, who was described as “very ugly” with pitted skin and a large nose, was also released this week.

Madeleine’s parents Gerry and Kate McCann, from Rothley, Leicestershire, are employing two retired British policemen to continue the search for their daughter.

The former officers — ex-RUC detective inspector Dave Edgar, (52) and ex-detective sergeant Arthur Cowley (57) — scoured thousands of pages from the official Portuguese case files looking for clues. They put the three reports of a suspicious stranger hanging around the McCanns’ apartment together with two sightings of a man carrying a child away from the flat on the night Madeleine vanished.

Mr Mitchell said there was a good response to Thursday night’s programme — Madeleine Was Here — which was watched by 2.6m people on Channel 4.

He said: “The investigative phone line has had at least 50 calls since the documentary.

“It’s a very encouraging response because there is real, new information being given in some of these calls, information that the investigators are now able to set to work on.

“Some of the calls are coming from Portugal, and that’s exactly where we need the information from.

“We will not go into detail but the investigators are very pleased with that response.”

He added: “Many of the calls are offering real information that’s potentially significant and can be worked upon. It’s not speculative or vague.”

The documentary will be shown by Portuguese broadcaster SIC on Monday and negotiations are under way to air it in other countries.