Speaking to the Standard, the Labour leader appealed to MPs and party members to “focus on the future, not the past” and offer a “credible alternative” to the Tories, after the Corbyn years.
With MPs on the Labour Left hostile to his leadership, Sir Keir said the party had to turn its attention outwards and “speak to and for the whole country”.
Sir Keir is under pressure to make his first in-person conference speech a success, with Labour having trailed the Tories in the polls for most of the time since he became leader last year.
As he prepared to head to Brighton, he said: “We need to show the country that we are a government in waiting with the hunger to win.”
Hailing Labour’s record of creating the NHS, the minimum wage and investment in schools and hospitals, he added: “We’re proud of what Labour has achieved in Government.
“But as Sadiq Khan has shown twice, with his positive vision for London, we win when we focus on the future, not the past.”
However, he is caught in a row over his attempts to change the leadership election rules from one member, one vote, which saw Jeremy Corbyn take over and lead Labour to election disaster in 2019.
Leftwinger Diane Abbott tweeted that the rule changes “will make it easier for the right to dump [Sir Keir] when the time comes”.
He added: “Labour will focus on providing security and opportunity to working people across the country, creating a society where everyone can make a contribution whatever their background.
“We will put the voter at the heart of everything we do, refocusing our attention on hard working families and offering up a credible alternative to this failing Tory party.”