One senior Lib Dem MP even suggested Mr Clegg had still to prove himself as leader and needed to listen more to activists' concerns.
Delegates at the party's annual conference in Bournemouth have been alarmed by his talk of "savage" cuts and the possible need to ditch the promise to abolish tuition fees.
In a barely-veiled critique of Mr Clegg's strategy this week, work and pensions spokesman Steve Webb said: "I think we have overdone the despair."
He added that the party would not win votes by being "too much hair-shirt" and bluntly opposed a move to means-test child tax credits - as suggested by Mr Clegg.
Lib Dem environment spokesman Martin Horwood became the latest MP to cross Mr Clegg over tuition fees, insisting the policy to scrap them should be made "stronger and clearer".
His comments were loudly applauded by delegates in the conference hall. Charles Kennedy, the popular former leader, has also raised concerns about the move.
Vince Cable, the party's highly-respected Treasury spokesman, was also angrily confronted by senior colleagues about his tax reform proposals today.
Frontbenchers have admitted publicly that they were not consulted about yesterday's announcement of a new "mansion tax" on properties worth more than £1 million.
According to The Times, Mr Cable was told by one that the policy was "complete codswallop".
Mr Clegg was not in attendance and his office declined to comment on what it described as a private meeting of the parliamentary party.
Senior Lib Dem MP Evan Harris used an address to the conference hall to state Mr Clegg had not yet proved himself as a "great" leader.
"I think Nick is a really great guy and a good leader," he said.
"But good Liberal Democrat leaders only become great leaders, as they all do, when they recognise it's the party that makes the policy.
"It makes the manifesto from that policy. And I expect Nick will soon be recognised as a great leader."
Mr Clegg has angered many within his party with warnings that they need to be "realistic" about what can be afforded given the dire state of the public finances.
He has appeared to acknowledge having gone too far by suggesting "savage" cuts were needed, however, dropping the word since it was picked up by the media at the weekend.
Delegates today approved his "Fresh Start for Britain" policy programme - but not without much criticism of details of the plans.
Susan Gaszczak, a member of the party's Federal Policy Committee (FPC), promised to fight to keep policies like tuition fees in the manifesto.
The row comes ahead of his keynote speech to the conference on the final day of the gathering tomorrow afternoon.
Earlier today, the Liberal Democrats called for the Government to start planning for the withdrawal of British troops from Afghanistan.
In a significant hardening of the party's stance on the conflict, delegates at its annual conference in Bournemouth demanded a new focus on bringing it to a conclusion.
However, senior party figures were at pains to insist that they were not calling for an immediate withdrawal of UK forces.
The new Lib Dem position comes amid signs the US will push for more British troops to take part in a military surge in the war-torn country.
General Stanley McChrystal, who commands Nato forces in Afghanistan, has warned in a confidential report that there is a risk of failure without significantly more personnel.
It was reported today that Britain was planning to send another 1,000 troops, taking its overall commitment to 10,000.
The Lib Dems passed an emergency motion tabled by grassroots members calling for "an end to the killing".
It urged the Government to "focus on concluding the Afghanistan mission and to report to Parliament in detail on progress towards a withdrawal".
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