The debate in the Labour party is described as a battle between principles and power. Some argue that in this leadership contest you can vote for one of these things, but not both. This is completely wrong.

Jeremy Corbyn and his supporters do not have a monopoly on principle. Many do, indeed, have firmly held principles, but they are not the only ones in our party or our movement.

This contest isn’t a choice between heartless pragmatism to win power and purity out of power. I’ve spent this campaign setting out the principles that drew me into the Labour movement and which I’ll keep on fighting for: ending inequality in the early years so every child has an equal shot at life; tackling low pay to build a real living-wage society and giving public sector workers the pay rise they need and deserve; and devolving decisions to communities and councils so people have power and control over their services and lives.

These are our Labour values. So, too, is championing a strong and vibrant economy, where we create the jobs and wealth we need to invest in public services and build a more equal society.

Labour was formed to be the voice of community organisers, civic leaders and workplace activists, whose fight against poverty and injustice involved organising for their values, their principles and their loved ones. These are the principles we must return to today to fight the Tories, who have never cared about inequalities of power, wealth and opportunity.

Instead, the Tories’ principles lead them to rebrand child poverty to cover up their failure to tackle it, to try to con people that George Osborne is offering them a national living wage when it’s nothing of the sort, and to drag our country out of the EU – which President Obama rightly said has “made the world safer and more prosperous” – to appease his backbenchers, not do what is best.

I utterly reject those principles. Yet there are also arguments being made in this leadership campaign – old rhetoric disguised as principle – that I reject too. I don’t think it’s principled to give up on electoral victory to make ourselves feel good. That would let down our voters, and millions of people in marginal seats who want a better Labour party.

I don’t think it’s principled to retreat to a position of withdrawal from the EU that Labour last held when we subscribed to the longest suicide note in history in our 1983 manifesto. Our future should be as an open, outward-looking country leading the reform of Europe, not the wrongheaded and damaging isolationism of Labour’s past.

There is also principle in winning and governing. It was the application of Labour principles that legislated for equality for LGBT people, that stopped the tolerance of failing schools, that attacked child poverty and reversed the European social chapter opt-out . I disagree with those who have nothing good to say about the Labour government – on principle.

Labour members should feel proud of the government they helped sustain for 13 years. It wasn’t perfect, but it changed Britain for the better. Winning is not selling your soul. Winning is not betrayal. Winning is the means of applying your principles.

When we talk about the great Labour achievements – the NHS, the minimum wage, Sure Start – we talk about what we achieved in government, not what we protested against from opposition. Yet every election we lose sees those achievements undermined.

The Tories will not believe their luck if Labour falls back into the politics of the 1980s. What they will fear, though, is an opposition that rejects this notion and regains economic credibility, an opposition that stands up to them when they abolish inheritance tax for the wealthiest while abolishing student grants for the poorest, an opposition that shows the kind of strong and unambiguous leadership over Europe. that they are incapable of providing because of their own party’s hang-ups.

In other words, an opposition that combines credibility with principle.