On Board PM's Special Aircraft, May 31 (IANS): Prime Minister Manmohan Singh Friday said his great regret as prime minister was that many bills had not been passed due to the "obstructionist" and "impatient" attitude of the opposition.

"The obstructionist role of the opposition increased in recent years. My great regret is that many important bills have not been passed (due to the opposition's attitude)," Manmohan Singh told journalists on board his special aircraft while returning from a five-day official visit to Japan and Thailand.

He said the opposition could not digest that the United Progressive Alliance (UPA) government had come back to power for a second consecutive term in May 2009.

"I can't tell you how I feel about the way UPA-2 has moved. I think there has been a great sense of continuity between UPA-1 and UPA-2. But it is unfortunately a fact that the opposition has become more impatient than ever before," he said.

"They never expected that we would win the election for UPA-1. But they were doubly disappointed when we won the election for UPA-2. Therefore, the obstructionist role of the opposition has increased enormously in recent years."

"It is my great regret that some very essential business of the house has not been transacted because of these animosities between the opposition and the government," he added.

The opposition parties, especially the Bharatiya Janata Party (BJP), have been gunning for the Manmohan Singh-led UPA-2 government for the scams that have taken place in its tenure since 2009.

The opposition has not let the two houses of parliament function during the recent sessions, putting up demands for resignations of ministers, including the prime minister.