Lucknow, May 1 (IANS): Uttar Pradesh minister Shivpal Singh Yadav's letter to US President Barack Obama on cabinet colleague Azam Khan being detained at Boston airport has triggered a controversy with opposition parties and civil society activists terming it objectionable.

In a petition sent to Governor B.L. Joshi, activist Urvashi Sharma termed the letter written by the Public Works Department (PWD) minister as unconstitutional and against diplomatic norms under which external affairs is a central not a state subject.

"This is highly objectionable and cannot be wished away," Sharma told IANS.

"No leader from any state can directly address the head of any other state like this."

Leaders cutting across party lines also come down heavily on Shivpal Yadav.

"This government and its ministers are known for their illegal and anti-constitutional acts so the letter written by Shivpal Singh Yadav comes as no surprise," said senior Bahujan Samaj Party (BSP) leader Naseemuddin Siddiqui.

Congress spokesperson Virendra Madan was equally critical and accused leaders of the state's ruling Samajwadi Party (SP) of "making a joke of their US visit".

"This is very sad for the state that they were represented by people who have made the state a laughing stock," he said.

"The aborted Harvard trip of the UP chief minister and his team has become a comedy of errors, thanks to people like Azam Khan and Shivpal Yadav," added Bharatiya Janata Party (BJP) spokesperson Vijay Bahadur Pathak.

Chief Minister Akhilesh Yadav led a delegation of officials and ministers to Harvard Business School for a lecture on the successful management of the Kumbh Mela. However, the chief minister boycotted the lecture after Azam Khan was detained.

Fighting off the criticism, Ram Asrey Kushwaha, SP national general secretary, said that as a cabinet minister of a state as important as Uttar Pradesh, Shivpal Yadav was "well within his rights to write a letter to the US president".