Chief minister Mamata Banerjee on Tuesday made a surprise cabinet reshuffle amid murmurs it was meant to reward Trinamul leaders who had helped the party put up a good show in the Lok Sabha polls in the face of a BJP surge across Bengal.

“As no new minister is being introduced, there is no need for an oath-taking,” said a senior official.

Ministers Suvendu Adhikari, Bratya Basu, Soumen Mahapatra and Rajib Banerjee have been assigned additional portfolios. Two cabinet members, Binoy Burman and Santiram Mahato, have been stripped off their departments but retained as ministers without portfolio.

Subrata Mukherjee, who lost the Lok Sabha elections from Bankura, has been allocated Paschimanchal Unnayan Affairs — which covers the tribal region of Jungle Mahal and was with Mahato so far — in addition to his existing panchayat portfolio.

According to a notification, Suvendu will now oversee irrigation and water resources departments in addition to transport. Basu has been given additional charge of forest over and above science and technology. Mahapatra will oversee public health engineering along with environment.

The shuffle was seen as an indication that the chief minister wanted to acknowledge those who had worked hard in minimising the impact of the BJP wave that reduced Trinamul’s Lok Sabha seats to 22 from 34 in 2014.

Sources said Suvendu was rewarded as he had ensured two seats for Trinamul from Murshidabad — so far a Congress bastion. Similarly, Basu ensured a handsome lead in his Assembly segment of Dum Dum for Lok Sabha candidate Saugata Roy.

“Mahapatra ensured a lead from his area in East Midnapore despite the BJP’s rise in certain pockets of the district. So, he was rewarded along with Adhikari and Basu,” said a minister.

Banerjee was given charge of tribal development in addition to backward classes welfare. His elevation is linked to his efforts in north Bengal where he held more than 25 rallies. “Trinamul could not win any seat in north Bengal but the effort by Banerjee was noticed,” said a Trinamul insider.

Asked about Burman and Mahato, a source said: “Trinamul performed poorly in the districts of the two ministers. This is the reason the two were punished.”

Sujit Bose has been made junior forest minister in addition to his existing charge of fire and emergency services. “Bose could not secure a lead from his own Assembly segment… It isn’t clear why he was rewarded,” said a Trinamul MLA.