17/07/2015 06:01 BST | Updated 16/07/2016 06:59 BST

A Woman Leader Is Not Enough - Winning Matters, Which Is Why Liz Kendall Is Labour's Best Choice

Niall Carson/PA Wire

For 92 years, whether by accident or design, Labour had never managed to find a woman Chief Whip to organise our representation in the House of Commons. There were plenty of powerful women - from Ellen Wilkinson, to Barbara Castle, Betty Boothroyd, and a host of others - who would easily have carried it off, but in Government and opposition, the Chief was always a man. Until 1998 and then for nine years, Labour changed.

Labour today stands on the precipice of breaking down another 100 years tradition. Within just a few months, we have the very realistic prospect of a woman elected as leader of the party. Two of the four candidates in the race are women. Never again can it be said that Labour leadership campaigns are only ever dominated by men: a woman is just as likely to win this time.

But electing a woman leader is not enough. We don't just need a woman leader asking the questions at Prime Minister's Questions. We need a Labour woman answering them, week-in, week-out. We need a Labour prime minister. Take it from us three, Labour needs a leader with a core of steel, who won't always tell people what they want to hear, but will tell the truth about what our country needs. That's the kind of leadership that commands respect. In short, we need a woman determined to become Labour's next prime minister. And that is why we are backing Liz Kendall.

A woman Leader of the Opposition may challenge Cameron from the despatch box, but she has no power to make reform happen; to modernise public services; to create the conditions for businesses to grow and entrepreneurs to prosper. Only being able to win elections gives us the chance to make Britain fairer, stronger and more modern, better educated, better skilled, more progressive and more productive.

In Government until 2010, women and men Labour MPs voted to establish the minimum wage, pension credit and proper maternity and paternity rights. Women ministers across government helped to rebuild Britain after 18 years of Tory misrule, sometimes staying up through the night at our request to make sure that bills were passed and that our country was kept strong.

So we know from the history of our party that there is just one route to power for Labour: economic credibility. This is the acid test the British public judge Labour leaders by. Liz was the first to make this case, and her speech last week, ahead of the budget, explained how she is prepared to accept that fiscal responsibility is a Labour value, and that sound public finances are the work of Labour Governments.

Equally, our experience in government teaches us that if you wish to maintain public support, your promises must be credible. If you plan to improve living standards, you need to explain your actions as well as your aspirations. Simply repeating an ever bigger number - shifting up from 200,000 to 300,000 new houses for example - will not wash, if our credibility is in question. Saying things that might sound good to our supporters in a focus group is worthless if most people don't trust our ability to deliver it or pay for it.

Instead, we would advise Labour to make clear where it will prioritise scarce public resources.

It is to be admired therefore that Liz will put investment on early education ahead of spending on students who have already reached university.

Liz is taking the correct course: not trying to be all things to all people, but reaching beyond Labour's comfort zone. Honesty, being clear with the public and reflecting the priorities that matter for the future of the country is the fastest path back from defeat.

We know from our lives in public service: strong leadership matters. Losing elections has serious consequences, not just for our party, but more importantly for the people Labour works to help. Winning matters. That's why Liz Kendall is the best choice.

Jacqui Smith is a former home secretary and chief whip

Baroness Taylor is a Labour life peer and former chief whip

Baroness Armstrong is a Labour life peer and former chief whip