Prime minister Manmohan Singh, a reluctant birthday boy, turned 80 on Wednesday but will spend the day working as he has done in the past, officials said. The photo division is yet to upload the happy returns of the day celebrations at 7 Race Course Road. A shy PM was another comment at Vigyan Bhavan when Manmohan Singh rose to address the gathering.

Being a workaholic, the prime minister has shied away from celebrations but there have been occasions when he has cut a cake on board his special aircraft during foreign trips.

The prime minister will give away the Shanti Swarup Bhatnagar awards and Council for Scientific and Industrial Research (CSIR) awards on the organisation's 70th Foundation Day function. The prime minister is the president of CSIR, whose foundation day coincides with his birthday.

"He will work as usual (on his birthday)," an official commented. The celebrations will be a low key affair, they said.

The prime minister last week embarked on a series of bold economic measures, including allowing foreign direct investment in multi-brand retail and a cap on the number of cooking gas cylinders.

The decisions, including a hike in diesel prices, cost the government support of the Trinamool Congress.

However, the prime minister reached out to people in a nationally televised address last Friday and told them that the economic policy decisions had been taken in the country's long term interests.

He compared the vehement opposition to FDI in retail to the situation in 1991 when the government opened the country to foreign investment in manufacturing and said the opposition tactics had failed then and will fail now.

Manmohan Singh, who has been prime minister since 2004, had also weathered the political storm when the Left parties withdrew support to the government over the India-US nuclear deal during the UPA-I government.

Born in 1932 in Gah Begal village in what is now Punjab province of present-day Pakistan, Manmohan Singh's birthday falls on September 26 because his parents had given it as his date of birth to get him admitted in school. His family shifted to India during partition.

"September 26 is shown in the school records as my date of birth," Manmohan Singh had said when asked about it. The prime minister has celebrated his birthday mid-air on four occasions.

He had cut a cake on his 77th birthday while on board Air India One enroute to Pittsburgh from Geneva and had also done so last year on his flight back from Frankfurt.