Political leadership is about changing the public agenda. Keir Starmer has failed to sway public opinion on major issues. Nigel Farage has been a much more effective political leader, albeit for a fraudulent project. He successfully made the argument for leaving the EU against the conventional wisdom of the majority of the British political elite and political commentators.

Margaret Thatcher was in this sense also a highly effective leader. She defied the civil service, many within her own party and Cabinet, and wide sections of the public, and drove through a deliberate shrinking of the size and functions of the state, through tax cuts, privatization, curbs on local government, selling off social housing and more. Politicians today still hesitate to challenge assumptions about outsourcing of public services or pledging to lower taxes, in spite of the very different economic and demographic circumstances we face. The nationalization of British Steel and the return of the railways to unified public management are moves away from neo-liberal orthodoxy – but the water industry still seems a step too far.

Keir Starmer has proved incapable of engaging with the public. The Strategic Defence Review, published ten months ago, called for a ‘National Conversation’ on the multiple threats our country now faces and the response needed to meet them. But we have been told almost nothing since then, and the promised Defence Industrial Plan is still blocked by the Treasury’s refusal to fund it. He’s just delivered another speech on how to ‘reset’ our relations with the EU, which began with some splendid rhetoric and ended with a promise of ensuring better youth mobility, without attempting to explain the complexities of closer cooperation with our neighbours or the trade-offs between sovereignty and shared prosperity and security that we have to make. Worst of all, neither the prime minister or his chancellor have tried to engage the public on the hard choices to be made on public spending and investment in pursuit of sustainable economic growth.

This is partly a structural problem in British politics, given the confrontational character of parliamentary politics. Successive governments have failed to address the problems of social care since the Conservatives gave Steve Webb’s proposals lukewarm support and the Labour opposition attacked tentative proposals as a ‘death tax’. Opposition leaders instinctively attack down government proposals. Kemi Badenoch denies responsibility for Conservative actions in government two years ago, and blithely promises to cut taxes without explaining what services will be cut to pay for them. And she has attacked David Gauke for the crime of cooperating with the current government to address a problem – prison overcrowding – that the Tories funked in office.

So what should the Liberal Democrats be doing in this era of negative campaigning, nervousness about speaking hard truths to the public and fear of being monstered by the Daily Mail? We too have been nervous about getting out ahead of the conventional wisdom. The Financial Times caricatured us last week as ‘a tortoise party’, plodding on through local campaigns without attempting to reshape the national debate. The Greens swept past us in the local elections, particularly with younger voters, by talking about climate change and social justice – even though they didn’t explain how to pay for their promises. Three years at most ahead of the next election, we need to engage in the wider battle of ideas, and to demonstrate that we can back up promises with plans and budgets to put them into practice in a future coalition government.

British democracy is now threatened, by our outdated and over-centralised institutions, by public disillusion, by well-funded right-wing authoritarians and foreign intervention. There’s a lot we should be saying about why liberal democracy must be defended and reformed. Britain has become a much more liberal society over the past half-century, but liberal values are under attack by misogynists, authoritarians and anti-Enlightenment reactionaries, spilling over into Britain from the USA. We should be outspoken on the defence of liberal values for all members of our diverse society. We now face global economic disruption and rising security threats, and should be making the case for full recommitment to ‘Europe First’. Our economy is flat-lining and our left-behind regions, and we should be talking about the fiscal choices to be made by any government in raising investment and promoting sustainable growth.

We’ve proved that we’re good at community politics. Now we need to show that we’re capable of sharing government.

* William Wallace is LibDem peer, a former vice-chair of the Federal Policy Committee and convenor of the party's 1997 manifesto team.