Mr Shearer said all MPs had at least one significant portfolio and sent a clear message they must perform if they wanted to be rewarded. He said he would review the lineup after a year.
"With 34 MPs I need all my team contributing fully. Everyone has a significant responsibility. I have made clear that I will be looking closely at the performance of every MP and strong performers will be rewarded."
He said the portfolios on the front bench showed Labour's focus would be the economy, the environment and science under his "clean, green, and clever" vision.
Mr Shearer said Mr Cunliffe was left on the front bench because of his obvious talent and ability to take on National rival Steven Joyce in economic development.
Although Mr Cunliffe had taken some time to consider, Mr Shearer said he had accepted the original offer of the fifth ranking and portfolio. Mr Cunliffe would not confirm whether other offers were made.
Mr Cunliffe said it was important to contribute to Labour "and I'm looking forward to taking on Steven Joyce".
Mr Shearer said experienced hands were also necessary - former leader Phil Goff and his deputy Annette King will sit in the second row.
"Three of the top four slots are being held by people who have limited time on the front bench. This is a mixture of freshness and experience and we will rely on that experience."
Those not in the "shadow Cabinet" of the top 20 were left unranked and many were given significant portfolio areas in a clear attempt to help prevent any serious discontent.
Mr Parker said he would work well with Mr Cunliffe despite the leadership contest because they had worked together previously.
"National has made economic management the basis upon which they are to be judged and I intend to hold them to account."
Mr Shearer also demoted some MPs, some of whom were philosophical yesterday. Moana Mackey went from 18 to unranked but was delighted with the energy and climate change portfolios, saying she had asked for environmental areas. Ruth Dyson and Sue Moroney fell from the front bench to unranked.
WINNERS
Jacinda Ardern leaps from 19 to 4 to become the highest-ranked woman with weighty social development portfolio.
Nanaia Mahuta returns to the front bench the with education portfolio after supporting David Cunliffe in leadership race.
Shane Jones is back on the front bench with economic portfolios and is the highest-ranked Maori.
Su'a William Sio are Phil Twyford are second-term MPs not on the front bench but moved well up the ranks to 10 and 11 respectively.
Andrew Little and Kris Faafoi are unranked but given meaty portfolios of ACC and police as a chance to prove themselves.