Fielding, who currently features as a team captain on the BBC Two panel show, said that guests are now reluctant to appear on the programme because of former host Amstell's vicious presenting style.
According to The Sun, Fielding said that ex-Spice Girl Mel B had to be heavily persuaded to appear on the quiz, adding: "She was terrified, like we were going to really rib her."
He went on to say: "The problem is, I think Amstell ruined it for everyone. Everyone thinks they'll get ripped to shreds."
Ordinary Boys frontman Preston infamously walked out during an episode of Buzzcocks after Amstell began reading extracts from then-wife Chantelle Houghton's autobiography.
Vanessa Feltz has also previously revealed that she found Amstell's jokes towards her "deeply offensive and incredibly upsetting" when she appeared on the programme.
Fielding admitted that he thinks the show has become "cosier" since Amstell's departure last year, and picked out Terry Wogan as his favourite guest stand-in so far.
"[Terry] was the best host we've had," he said. "He was professional, funny, quicker than anyone else on the show. He shook everyone's hand, he knew everyone's name. It was pretty mind-blowing actually."
Wogan's episode is due to air on November 11.
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