The number of foreign tourists arriving in India dropped by 25% during the first three months of this year, largely because of fears about the risk of sexual assault, according to an industry survey.

The number of female tourists fell by 35% compared with the same period last year, with Indian tour operators reporting many cancellations from January to March following the fatal gang rape of a physiotherapist on a Delhi bus last December.

The figures from the Associated Chambers of Commerce & Industry of India (Assocham) are based on a survey of 1,200 tour operators and contradict the government's rosy picture of the tourism business.

For both January and February, tourism ministry figures showed an increase in the number of tourists and revenue from tourism, compared with the first two months of 2012. A month after the Delhi gang rape, the tourism secretary, Parvez Dewan, said: "So far there has been no adverse impact on tourism."

Since then, however, at least six foreign women have complained to police about being attacked or traumatised by men, mostly at tourist destinations, leading several countries, including the UK, to issue travels advisories for India.

Delhi police figures show a dramatic rise in reported crime since 1 January, with molestation cases up by 590.4% over the same period last year and rape cases up by 147.6%. The front pages of Sunday's newspapers carried a story about the gang rape of an 18-year-old male Delhi University student who had gone out to meet a Facebook friend.

Assocham's secretary-general, DS Rawat, said that while the government was banking on tourist dollars to help reduce the country's yawning current account deficit, the security situation was making foreign tourists bypass India for other Asian destinations such as Malaysia, Indonesia and Vietnam.

Despite the global economic slowdown, India earned $17.7bn (£11.6bn) from 6.6 million foreign visitors in 2012. Delhi aims to increase annual tourist numbers by 12% and double foreign exchange earnings from tourism by 2016.