Shadow chancellor John McDonnell has said he would be "ruthless" about managing spending and said his ambition is to restore credibility in economic debate.
On Friday, he admitted Labour has "a long way to go" to regain public trust on the economy, as he unveiled a new "fiscal credibility rule" which will guide future policies on taxation and spending.
The rule would bar a future Labour government from borrowing to pay for day-to-day spending and would require it to ensure that the national debt falls as a percentage of GDP over the course of each Parliament.
But it leaves open the option of borrowing to pay for investment in infrastructure like roads, railways, broadband and flood defences, which sparked Conservative claims that a Labour administration would plunge the country into billions of pounds more debt.
Speaking on the Today programme on BBC Radio 4, Mr McDonnell said: "What we want is a fair taxation system where everyone pays their way so we don't have any more Google taxes and all the rest of it where people can walk away from their responsibilities.
"Secondly that we invest in the long-term, and as a result of that we grow the economy, but the most important thing as well is that we share that prosperity as we grow the economy, and I think that's sound common sense.
"And it's been welcomed right the way across the business sector and from the trade unions. The wealth creators have welcomed it."
Mr McDonnell said Labour lost credibility because the party lost two elections, telling the programme: "Well there were some mistakes made, but to be frank, the last crisis was brought about because successive governments from Mrs Thatcher on were allowing bankers to create a casino economy.
"I criticised my own side New Labour for allowing some of that to happen as well."
He added: "I'm not just talking about restoring credibility of the Labour Party. I've got this ambition, I want to restore credibility in political economic discussion in this country overall, because I think at the moment people just do not trust, not just the existing Chancellor, but they do not trust those who are in charge of our economy in terms of the political decisions being made."
He told the programme: "Let me make it absolutely clear. I will be absolutely ruthless about how we manage our spending."
Mr McDonnell added: "It's not about cutting. It's about making sure you spend the money wisely, but in addition to that you make sure you have a tax system that's fair, and you grow the economy. Austerity is not an economic necessity, it's a political choice."