Washington (CNN) Following an op-ed from former US senators urging their current colleagues to defend democracy, former Sen. Alan Simpson warned of the growing partisanship in the body.

"You can see the bitterness that goes on," Simpson said in an interview Tuesday with Alisyn Camerota on CNN's "New Day." "You see the fact that if they're a Democrat, you just ignore them, or if they're a Republican, you ignore them."

He recalled how senators of different political affiliations would laugh and sit together in a dining room that has since become a storage room when he was in office, according to Simpson.

The former Republican senator also pointed to his previous working relationships with former Democratic senators on the Senate Judiciary Committee including Joe Biden and Ted Kennedy.

Simpson, who represented Wyoming from 1979 to 1997, was one of 44 former US senators to sign a bipartisan op-ed in The Washington Post published Monday warning "we are entering a dangerous period" and urging current and future senators to be "steadfast and zealous guardians of our democracy."

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