Six Trinamool Congress Ministers on Friday submitted their resignations to Prime Minister Manmohan Singh who expressed sadness over the ally's decision in protest against allowing FDI in retail.

The Ministers -- Mukul Roy, Sudip Bandhyopadhay, Sultan Ahmed, Sougata Roy, Sisir Adhikary and C M Jatua -- went to the Prime Minister's 7, Race Course Road residence to submit their resignations.

While receiving the resignation letters, the Prime Minister said he was "sad" that they were quitting, Bandhyopadhay told reporters later.

Mukul Roy was the only Cabinet Minister among the six holding Railways portfolio since March.

Bandhyopadhyay was Minister of State for Health, Ahmed was MoS for Tourism, Sougata Roy was MoS Urban Development, Adhikary was MoS Rural Development and C M Jatua MoS Information and Broadcasting.

Trinamool Congress chief Mamata Banerjee on Wednesday had announced her decision to withdraw support to the UPA protesting the Centre's decisions to hike diesel prices, withdraw subsidy on cooking gas and allow FDI in multi-brand retail.