Also speaking to Kuenssberg, McFadden said the episode had damaged the government, conceding the appointment had “turned out to be the wrong decision”.
But he urged Labour MPs not to try and oust Sir Keir over the episode, adding it would damage the economy and the UK’s “international reputation”.
“I know that when it’s a rough week it’s easy to reach for lever, change the leader, change the leader’s chief of staff, and think that will fix it,” he said.
“I think the country’s had pretty good experience in the last 10 years, and has tested to destruction the idea that changing the prime minister solves the country’s problems. It doesn’t.”
He also called for Lord Mandelson to return a pay-off he received after his sacking, or donate it to an “appropriate charity”.