"We demand an answer to the spending on the Singapore trip. As it was undertaken on public money, the state has to answer what is the outcome of the visit and how much money was spent. And if it is a sponsored trip, then who sponsored it and why," Sinha told reporters.
Banerjee is on her first foreign visit to Singapore after assuming office in 2011, with an agenda to attract investment for the state.
The chief minister is accompanied by Finance Minister Amit Mitra, Chief Secretary Sanjay Mitra, actor-turned-party MP, Dev, and a group of industrialists. "If after coming back, the state government and the chief minister don't answer our queries, we will file an RTI to seek the answers," Sinha said.
Sinha had earlier mocked the visit as a "holiday trip" which would not bear any fruitful result.
He also said the party would announce within a day or two its candidates for the September 13 bypoll for two Assembly constituencies.