Shearer insists he is doing good job as leader as party prepares for conference.
Labour is proposing to make future leadership contenders take a "behaviour pledge" to try to prevent messy cannibalistic attacks on each other during leadership races.
The change is among changes party delegates will consider at its conference this weekend following a major review of the party.
A change to give the party members and affiliated unions a vote on the leadership will include new rules under which a leadership contest is held - including a "behaviour pledge" for contenders and a spending cap on any advertising in a leadership contest.
Party President Moira Coatsworth said the new leadership process was far more public than the previous process, which had largely happened behind the closed doors of caucus.
"So there will be expectations of candidates' behaviour in that context. People's behaviour in that competitive environment sometimes isn't helpful, and it's making clear what the expectations are."
Labour's deputy leader Grant Robertson said one of the concerns party members had raised about the new leadership system was the experience overseas, such as primaries contests in the United States which could be bitter and characterised by personal attacks - a messy situation Labour is keen to avoid.
"One of the topics was ensuring it remained positive, rather than negative, for the party."
The conference will also work out details of future leadership contests, likely to be similar to the battle in December 2011 in which David Cunliffe and David Shearer travelled the country to speak to the party members.
Under the changes members will get a 40 per cent share of the vote for leader - the same as caucus. Affiliated unions will get 20 per cent.
The conference is also expected to change the ways in which a leadership vote can be forced - the review team had proposed requiring a two-thirds vote by caucus to trigger a leadership contest at any time other than a regular post-election confidence vote in caucus. However, that threshold is likely to be lowered to a simple majority of caucus, or 55 per cent.
It is also the first annual conference for Labour leader David Shearer who has had to defend his record after a spate of blogs questioned whether he should stay on as Labour leader. "I am doing a good job as leader because Labour has come up in the opinion polls and National has come down."
He said the polls were trending upwards for Labour and the gap with National was at its narrowest in five years. "That's a pretty good record. I'm very happy with where we're going." He said the conference was an opportunity for him to set out Labour's direction and values.
However, Prime Minister John Key yesterday took the opportunity to repeatedly needle Mr Shearer in Parliament. In response to questions about employment and jobs, Mr Key said that one job everybody was wondering who would fill was that of Labour leader.
On their way into the caucus meetings, other MPs were quick to defend Mr Shearer. MP David Parker said Mr Shearer had been a good leader and would deliver the goods at the conference. Andrew Little and David Cunliffe again ruled out any leadership challenge.
* Leader is elected by votes from caucus (40 per cent), members (40 per cent) and affiliates (20 per cent).
* Leadership contest can be triggered by a leader stepping down, a three-yearly confidence vote by caucus, or at any other time if a percentage of caucus call for a contest. For the last mentioned, delegates will decide whether that should be two-thirds of caucus, a simple majority or 55 per cent.
* Rules will be developed, including candidate spending limits and a "behaviour pledge".