David Cameron has hailed his new-look top team, insisting he has put the right people in place to kick-start the flagging economy.
The Prime Minister said the reshaped Government "meant business" and every department would be focusing on projects to boost growth.
His speech in the Commons came as the row over his decision to remove Justine Greening from the transport brief still raged.
London Mayor Boris Johnson stepped up his attack by demanding that Mr Cameron extend his pledge not to build a third runway at Heathrow beyond the 2015 general election.
Labour leader Ed Miliband used the first Prime Minister's Questions since Parliament returned to mock the reshuffle, branding it "the same old faces, the same old policies".
"We saw a reshuffle yesterday. He brought back David Laws, he promoted the culture secretary who should have been sacked, and he left in place the part-time Chancellor that the whole country knows should have been sacked," Mr Miliband told MPs. "It is the same old faces, the same old policies, a no-change reshuffle."
But Mr Cameron said he was determined to ensure his Government's focus was on restoring growth. "It is not that there are two economic departments in our country," he said. "I want every single department to be about the economy. I want the transport department building roads, I want the communities department building houses, I want the culture department rolling out broadband. I want the agricultural department backing British food. This is a Government that means business and we have got the team to deliver it."
He also dismissed suggestions the Liberal Democrats were unhappy with some of the appointments - which were seemingly designed to appease unrest on the Tory right wing. "The fact is that in spite of all the economic difficulty, this is a strong and united Government," Mr Cameron said. "And in spite of all the opportunity, this is a weak and divided Opposition."
Mr Miliband highlighted the move to give former justice secretary Ken Clarke a roving brief on economic matters, saying it amounted to a "job share" with Chancellor George Osborne. Referring to criticism of Mr Osborne's role overseeing political strategy, he said Mr Cameron had "come up with an ingenious solution to the problem of his part-time Chancellor - he's appointed another one".
But a clearly stung Prime Minister accused Mr Miliband of not being "butch" enough to control shadow chancellor Ed Balls, amid reports of friction between the two men. "I've got my first choice as chancellor, you've got your third choice as shadow chancellor (Ed Balls)," Mr Cameron said. "And apparently you still have to bring him the coffee every morning." He added: "That's just how assertive and butch the leader of the Opposition really is."