The Liberal Democrat party's European Union spokesperson said he accepted the government has a mandate to leave Europe. However, he wanted to be sure it didn't "throw the single market baby out with the EU bathwater".
He also said he believed the British prime minister would easily win a majority in the House of Commons if a "sensible, coherent plan for Brexit" was presented.
However, he criticised Theresa May's Brexit timetable as a "fundamental tactical error", and claimed the decision to trigger Article 50 in March 2017 was "frankly just to throw red meat to her backbenchers".
"I think Theresa May has already made a fundamental tactical error by saying… that she's going to trigger Article 50 in March of next year because she has already in doing so lost about a quarter of her negotiating timetable," he told BBC's The Andrew Marr Show.
"As anybody in Europe will tell you, nothing is going to meaningfully happen until the end of the year , after the German elections."
Germany is set to hold a federal election in 2017. Germany's law requires the election be held between 27 August and 22 October.
Clegg also confirmed that he would be pushing for a parliamentary vote on the terms of Brexit to ensure the government doesn't "throw the single market" away.
"While the government has a mandate to pull us out of the European Union, they don't have a mandate how to do that and that is why it is important the government strengthens its own hand and also subjects its own ideas to the scrutiny of parliament before they go elsewhere in Europe," he said.
"It is an attempt to ensure that as the government ensures its mandate to pull us out of the EU, they do so in a workable way, a legal way and crucially in a way that doesn't throw the single market baby out with the EU bathwater."
He also claimed denying MPs a free vote on the subject would be "absurd" and against the British principles of a "representative democracy".
"We live in a representative democracy where, of course, the government has a mandate to pull us out of the EU, but it doesn't have the mandate without any scrutiny or account from parliament," he said.
"To do otherwise, it is as absurd as suggesting when a party wins an election after that it should be able to do exactly what it likes and Parliament should have no role whatsoever, we don't do that in our democracy."
'Brexiteers' in 'Brenial'
He also launched a scathing attack on the Leave campaign, slamming Nigel Farage, Boris Johnson and Michael Gove as a "cast of opportunists and chancers".
He said: "What is coming back to haunt the Brexiteers, are people like me who are called 'Bremoaners'. I think they are in a state of Brenial, they are Breniers, because they are denying the mendacity of their original campaign.
"The Remain campaign in my view was a listless campaign. While it made some exaggerations, it didn't claim we would get £350m in the NHS every week, it didn't claim there was a Utopia awaiting us if we leave the EU, it did not claim eight million Turks would come here.
"If they had spelled out with one voice, Farage, Gove, Johnson, if all this cast of opportunists and chancers had actually agreed on what Brexit was, then they would have a mandate to implement that plan.
"What's worrying is they still don't have a plan or agree on about what Brexit means in practice."
The Lib Dems are pushing for a second referendum to decide the terms of a final Brexit deal.
Speaking at the party's autumn conference last month, Clegg accused the Tories of being "up a Brexit creek without a paddle, a canoe or a map – they have absolutely no clue".
He also warned leaving the European single market would do "untold damage" to the British economy.