The Liberal Democrat leader has praised Mr Cameron for forming a coalition government but said his main political legacy would be taking the UK out of Europe to the "huge detriment of future generations".
Tim Farron said that the former prime minister had "demonstrated a capacity to think above and beyond tribal politics" by creating the first post-war coalition government between 2010 and 2015.
He also praised Mr Cameron's qualities of "personal courtesy, humour and thoughtfulness" but said the former leader would be mainly remembered for taking the UK out of the EU in a damaging "gamble".
He has lots of things that he should be proud of but sadly his legacy will be one of accidentally removing us from our closest friends and neighbours in Europe.
He took a politically motivated and short-termist gamble with our country's future, and lost to the huge detriment of future generations. He now leaves the rest of us to pick up the pieces.
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.