John McDonnell addressed Labour supporters at a rally in Liverpool, ahead of the General Election on December 12 and struck back at former colleague Ian Austin after the ex-MP called on members of the public to reject Jeremy Corbyn in favour of Boris Johnson at the polls.
Earlier Mr Austin, who is not contesting the Dudley North seat he has held since 2005, issued a blistering attack on Mr Corbyn – telling the Express & Star newspaper: "I must do everything I can to stop Jeremy Corbyn from getting into power."
The shadow chancellor claimed Mr Austin was "employed by the Tories", adding: "What else do you expect him to do in an election campaign where you're employed by the Tories, you speak on behalf of the Tories. That's what this was about this morning."
After a turbulent start to the election campaign for the two main parties, Labour and the Tories sought to shift the focus to the economy instead.
Mr McDonnell said Labour would invest £150 billion in schools, hospitals, care homes and council housing over five years and he pledged an "irreversible shift in the balance of power and wealth in favour of working people".
"That means change, real change, and it means investment on a scale never seen before in this country and certainly never seen before in the north and outside of London and the south east," he told supporters in Liverpool.
"To achieve that objective it also requires, therefore, an irreversible shift in the centre of gravity in political decision making as well as investment in this country from its location solely in London to be relocated to the North and regions and nations of our country."
Chancellor Sajid Javid, speaking in Manchester, said the Conservatives would increase borrowing to pay for new infrastructure.
Heralding new fiscal rules for a "new economic era", he said: "While we must retain spending if we want growth to continue and get stronger in the future, then we need to invest in it. Taking the opportunity offered by those historically low borrowing rates."