Three former cabinet ministers – Energy Secretary Ed Davey, Business Secretary Vince Cable and Treasury Secretary Danny Alexander – were among more than 40 Lib Dem MPs to lose their seats.
Mr Clegg held his, but said he would discuss his position as party leader with colleagues reports BBC.
As of 0915 BST the party was holding eight seats, and had lost 46.
It had 57 seats in the House of Commons in 2010.
Other senior Lib Dems to topple were former schools secretary David Laws, former party leader Charles Kennedy and former deputy leader Simon Hughes.
Speaking at the result of his Sheffield Hallam count, Mr Clegg said: “It is now painfully clear this has been a cruel and punishing night for the Liberal Democrats.
“The election has profound implications for the country and for the Liberal Democrats.
“I will be seeking to make further remarks about the implications of this election – both for the country and for the party that I lead and for my position in the Liberal Democrats – when I make remarks to my colleagues in the Liberal Democrats later this morning when I return to Westminster.”