The shadow Treasury minister, in an article for the Guardian, said he wanted to “unleash” the Labour movement to win its first general election since 2005.
Mr Lewis said he wanted to have the opportunity to “win back” the trust of the electorate in Labour’s traditional heartlands, where large swathes of voters deserted the party in favour of Boris Johnson’s Conservatives at the election.
“The truth is that while making a clear break with the New Labour era in terms of policy and personnel, the party was never able to communicate this to voters in our heartlands,” said the MP of four years.
“When trying to persuade them of our radicalism and sincerity, we often had the legacy of the 2000s thrown back in our faces.
“Persuading voters that we understand the sources of their long-held resentment and frustration, of their disappointment in how Labour has conducted itself since the 1990s, will be the first step towards winning back their trust.”
Rachael Maskell, MP for York Central, has been quick out of the blocks to endorse Mr Lewis for leader.
The contest to succeed Mr Corbyn has yet to officially start but a number of other candidates are expected to declare in the coming weeks.
Shadow business secretary Rebecca Long-Bailey is said to be considering running, while shadow Brexit secretary Sir Keir Starmer, Wigan MP Lisa Nandy and arch-Remainer and Tottenham MP David Lammy have all expressed interest.
She said Mr Corbyn was “badly let down” and, while she declined to name anyone specifically, she said “people know who it is that I’m talking about”.
It was put to Ms Thornberry on BBC Radio 4’s Today programme that she was kept off the airwaves for much of the election campaign, as she was asked what it has been like “dealing with the Corbyn regime”.
“See, I don’t recognise that caricature,” she said. “I was obviously available, and it was a matter not for me but for those making decisions during the election as to whether or not I was used, and it was obviously a matter for them and I’m a team player so I went off and worked in marginal seats, which I thought was an important thing to do.
“I think that Jeremy has been badly let down. I think that Jeremy has been badly advised.
“And I think that there have been a number of mistakes made between 2017 and 2019 that undermined him so fundamentally. As I say, I think he was let down.”