Surveys of India's tiger population that have cheered conservationists by reporting sharp rises in numbers may have exaggerated, an investigation claims.

The survey team may have double-counted scores of tigers by misinterpreting camera trap photographs, according to an analysis of the counting method.

Narendra Modi, India's prime minister, in July hailed an “historic achievement” after tiger numbers were reported to have risen from 2,226 in a 2015 survey, to 2,967 this year.

Officials said they were confident in the numbers because more than four-fifths of those counted had been photographed by 26,000 cameras set up in known tiger habitats.

But an analysis by experts for the Delhi-based daily Indian Express has now claimed the earlier 2015 survey had over-counted tigers by as much as 16 per cent.