Labour backbencher Dan Jarvis is to fuel rumours over his leadership ambitions by setting out his vision for winning back the electorate.
In a keynote speech on economic policy, the Barnsley MP will dismiss the "false choice" between condemning the legacy of Tony Blair and Gordon Brown and endorsing it in full.
He will argue that the party did not do enough in government to address fears about large-scale migration and tackle inequality.
The intervention comes amid mounting speculation that there could be a challenge to Jeremy Corbyn this summer - especially if May's elections suggest Labour is failing to make headway against the Tories.
Mr Jarvis, a former soldier, is regarded as one of the most likely candidates and is believed to have been raising funds.
Delivering his second wide-ranging speech in a week, Mr Jarvis will tell an audience at think-tank Demos: "Let's be frank – New Labour's approach wasn't enough. It didn't get at the root causes.
"New Labour didn't see with sufficient clarity the downsides of globalisation. They knew it meant cheap consumer goods. But they didn't recognise that too often it meant cheap labour too."
However, he will urge the party not to abandon its record in government altogether.
"It's a false choice to say we must either champion Labour's record in government or denounce it. The truth is we should defend our achievements and learn from our mistakes. To anyone outside Westminster, that's common sense," he will say.
Highlighting the economic divide between the North and the South, Mr Jarvis will point out that the average income in Barnsley is £100 a week less than the average income in Barnes in London.
"I believe this gap matters. It's bad for our economy. It's bad for our communities," he will say.