Labour leader Jeremy Corbyn said he wished David Cameron "all the best for the future", adding he got on well with him on a "human level".
Mr Corbyn thanked the former prime minister for the "courtesy" he showed him.
He added: "We should respect people who move on to do something else with their lives. I want to wish him all the best for the future."
Speaking as he arrived for a private dinner with the TUC general council in Brighton, Mr Corbyn also joked about the "advice" Mr Cameron said his mother would give him about what to wear.
He also said he wanted to wish him well as a fellow cyclist, but joked he wasn't going to say "on yer bike."
Cameron said he would stay on as Witney MP after resigning as PM - but he said in practice it was an impossible switch.
The former prime minister has stepped down from his position in parliament as he resigned his seat as the MP for Witney.
He rose to lead the country before an equally dramatic downfall after failing to persuade the public to vote to remain in the EU.