Leading article: Clegg's promises that will be hard to keep

As the leader of a party which has traditionally had to try hard to get a public hearing, Nick Clegg is used to making big, bold statements. And the Deputy Prime Minister certainly makes some big, bold statements in his interview with this newspaper today. Mr Clegg claims the coalition Government will succeed where the previous Labour administration failed, namely by reducing poverty and increasing social mobility.

He adds that the coalition's programme will be attractive to those who "used to invest their hopes in New Labour". This is a message aimed, to some extent, at the wider Liberal Democrat movement which, despite giving its seal of approval to the coalition deal at a special conference last month, is still rather uncomfortable with the party sharing the Commons benches with the Tories. It is also designed to appease those left-inclined voters who cast their ballots for the Liberal Democrats in the general election only to see Mr Clegg's party help David Cameron into Downing Street.

But intelligently pitched as Mr Clegg's pledge might be, it is going to prove hard to deliver. Labour found it immensely difficult to make modest reductions in poverty levels during its 13 years in power. And that was, for much of the time, an environment of bumper tax revenues. Mr Clegg is promising to do better in an era of fiscal austerity.

The coalition has said it will remove some tax credits from prosperous families as one of the first steps in cutting public expenditure. But the inescapable fact is that the primary beneficiaries of public spending are the less well-off. And the most deprived parts of the country are disproportionately reliant on public sector employment. Reducing the deficit will inevitably mean pain for poorer communities.

The coalition has polices which, it argues, will refresh parts of our society that New Labour failed to reach. This includes a radical schools policy and a goal of taking low-income earners out of the tax net. These policies have their merits. But the advances that free schools and better incentives to work promise will only happen over the longer term. Public-sector job cuts and reductions in local services will impact much sooner.

Mr Clegg promises special help to areas that will be hardest hit by deficit reduction. This is indeed likely to be the crucial test for the Liberal Democrats. There are many people in the country who are giving this Government the benefit of the doubt because of the presence of the Liberal Democrats. The hope is that they will be a moderating influence on the Conservatives. If, by the time of the next election, Mr Clegg is seen to have failed to safeguard the interests of the most vulnerable, the consequences for his party could be disastrous.

It remains to be seen what the departure of David Laws from the Cabinet will mean for the Liberal Democrats' influence within the Government. Mr Clegg argues that the coalition has emerged stronger because of the manner in which it pulled together during the furore over the expenses of the Chief Secretary to the Treasury. But Mr Laws was unusual in Liberal Democrat circles because he was strongly convinced of the need to bring down public spending on an accelerated timetable. That was why his loss was so mourned by the Conservative wing of the coalition. Both sides were sorry to see him go. But Mr Laws was one of the connecting sinews of the coalition. It is hard to see how his departure can possibly make the alliance stronger in the face of the inevitable strains which are to come.

Bold and striking promises have their place in politics. But Government is, ultimately, about delivery. Mr Clegg understands the first part. We wait, with some trepidation, to see whether he can make good on the second.