Nick Clegg has used his first Commons clash as Lib Dem leader to urge Gordon Brown to do more to help hard up families who face higher fuel bills.
Mr Brown said he hoped Mr Clegg could work with the government.
He called on the PM to press gas and electricity companies to "end the scandal of the poorest families paying the most for their energy needs".
Mr Brown welcomed Mr Clegg to his new job, saying he hoped the two parties could work together on "major issues".
Conservative leader David Cameron said he also wished the new leader well.
In the first question time of 2008, Mr Clegg warned that an estimated 25,000 people were predicted to die from the cold this winter.
He said "countless British families face fuel bills of £1,000 or more for the first time" this year.
Mr Brown said: "We will do everything in our power to avoid fuel poverty in this country."
In his welcome, Mr Cameron told Mr Clegg: "You are the fourth Liberal Democrat leader I have faced and I wish you well - though not that well."
Ahead of his Commons debut Mr Clegg told the BBC that rather than worrying about addressing MPs he was "looking forward to the next months and years".
"I'm incredibly optimistic about the prospects for the Liberal Democrats. This Wednesday morning ritual is only one small sort of stitch in that wider pattern.
"I think it's important in Westminster terms - I'm not sure if that many members of the public really pay that much attention to it, but it's certainly important in terms of our parliamentary ritual and procedure."
Sir George Young, Tory chair of the Commons standards and privileges committee, said the Lib Dem leader should "be relatively pleased" with his performance.
"He dealt with the heckles of 'bring back Vince, bring back Ming' and the sort of derisive laughter," he told BBC Radio 4's World At One programme.
"He played it safe - he chose fuel poverty which is a good safe area to go on. He didn't risk any jokes that might have fallen flat."
Lib Dem Malcolm Bruce said: "He played safe but it was a perfectly good, competent start. It was on an issue which is topical, given the season and the weather."
Ex-Labour minister Keith Vaz said Mr Clegg was right to stick to one subject, rather than produce a "shopping list" of gripes.
The weekly joust between the prime minister, leaders of the opposition and MPs, is a notoriously rowdy affair in which members have to almost shout to get themselves heard.
Unlike the prime minister and leader of the opposition, the Lib Dem leader does not have a dispatch box from which to ask his questions.
Mr Clegg also suffers from having only two questions compared with Mr Cameron's six questions.
And in both cases the occasion is structured in a way which means the prime minister always has the last word in any exchange.
As new leader Mr Clegg's initial task is to raise his public profile - there is widespread debate about the importance of the Commons questions sessions on voters' views.
Vince Cable, who became acting leader after Sir Menzies Campbell quit, received widespread praise for his witty contributions to question time.
But the experience of past Lib Dem leader Sir Menzies Campbell - and Iain Duncan Smith for the Conservatives - suggests that poor performances can damage a leader's standing with their own MPs.