Gordon Brown has attacked Tory leader David Cameron at a meeting of the Parliamentary Labour Party.
Mr Brown was said to have been in a relaxed mood
In his first appearance before Labour MPs during the leadership campaign, he said the grammar schools row showed that Tory policy ideas "unravel".
Party sources said about 200 MPs were at the event, which was also addressed by all six deputy leadership hopefuls.
One MP said there were many questions about campaigning; another said Iraq barely featured in the discussions.
The chancellor spoke for about 10 minutes, then took questions for a further 15 minutes.
He was reported to have hinted he may look at a more inclusive approach to policy development.
This could involve an enhanced role for the Parliamentary Labour Party and Labour's National Policy Forum.
Mr Brown is to replace Tony Blair as Labour leader and prime minister from 27 June.
One Labour junior minister, who was at the central London meeting, told the BBC that Mr Brown said reports of disagreement among senior Conservatives showed there are still tensions in the opposition party.
The decision not to support new grammar schools has upset some Tory MPs.
Mr Brown said David Cameron has had some success because of his presentation, but his party had not gone through a genuine process of renewal.
One backbencher said Mr Brown was "much more relaxed than usual".
He was said to have begun by making a light hearted quip about how there were no longer any Blairites or Brownites, just a united party.
Speaking after the meeting the Treasury minister Stephen Timms said Mr Brown was "good, very good", and foreign office minister Lord Triesman said: "He left a very cheerful group of people up there".