Terming the meeting as "political misadventure", Jaitley wanted Singh and the Congress to explain the context of attending the dinner hosted by suspended party leader Mani Shankar Aiyar for Pakistani diplomats.
He said the main Opposition party is expected to follow the national policy, which states that terror and talks cannot go hand-in-hand.
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"Is (the) main opposition party not part of the State?" he asked.
Jaitley said that if anyone defies the national line, he should be prepared to answer questions.
"It is a political misadventure, it has a political cost," he said.
Jaitley addressed a press conference hours after Singh asked the Prime Minister to apologise to the nation for setting a "dangerous precedent".
He wanted the former prime minister to explain what transpired at the meeting and went on to defend his government's track record of fighting terror, saying no government in the past has a track record this government has in fighting terrorism.
In response to Singh's demand for apology, Jaitley further said people who have violated the national policy of talks and terror not going hand in hand should apologise.