Kicking off our local election special, former adviser to the ODPM Paul Hackett surveys the all-important battleground for the core city vote

Thursday 4 May is local election time again and the core cities will be centre stage. All the London borough seats will be contested as well as one third of the seats in 144 other local authorities, including 36 metropolitan boroughs. The local elections will be the first leadership test for the leader of the Conservative Party, David Cameron, and the new Liberal Democrat leader, Menzies Campbell, and perhaps the last campaign for Tony Blair.

All three parties will be taking a long hard look at how their respective vote holds up in the big cities, especially in London and Birmingham where there are likely to be shifts in the power balance.

The top 56 cities in England account for 60% of the national vote and dominate the debate over housing, crime, health and education. If you add in the outskirts - those areas from which people travel into work - these cities represent nearly three-quarters of the population and most of the employment growth. The cities have never been more politically important and will form the main battleground for the next general election.

The Conservatives are desperate to win back support in the core cities and hope to kick-start their revival at the May elections. Urban chic, not green wellies, is central to the "Cameron project". Tory activists are targeting marginal city seats and the leader has told his party that they "need new votes, not just the core vote, from people living in our great cities".

Labour meanwhile has made much play of the recently published reports showing how the cities have dramatically improved their performance, including the ODPM's State of the English Cities study by a group of city experts led by Professor Michael Parkinson, and the chancellor's Budget report on the importance of cities to regional growth. The minister for local government and communities, David Miliband, has announced he is embarking on a second round of city summits and has floated the idea of giving the large cities powers over regeneration, housing, planning and skills training. More devolution is proposed for London, and deputy prime minister John Prescott has announced a third Sustainable Communities summit next year on the role of cities in the global economy.

The Liberal Democrats also acknowledge the political significance of the urban vote and will be hoping to build on their previous city-wide successes at local elections. Indeed, it has been the LibDems who have historically made the most ground at city council level, although they have struggled to convert local support into seats at Westminster. In 1975 the Tories, for example, held a 52% share of all metropolitan borough seats, compared with 6% for the LibDems. By 2004, the Tory share had collapsed to 22% and the LibDems risen to 24% (with Labour rising over the same period from 37% to 48%).

Although the LibDems are still a long way behind Labour, they are catching up in some of the major cities. They have gained control in Leeds, Newcastle and Liverpool and are running close in Sheffield, Manchester and Birmingham. Indeed, the LibDems now control six metropolitan councils and London boroughs combined, compared with 12 for the Conservatives and 31 for Labour.

At the other extreme, the Conservatives control 132 shire counties and districts, compared with 20 for the LibDems and 28 for Labour. The threat of unitary councils in the English regions is likely to exacerbate this trend and stoke up the town/country political divide, not least within the Conservative Party itself.

The Tories took more councils than any other party at the 2005 local elections and have the most council seats across Britain. But Labour is by far the largest party in the cities. For Cameron to reconnect his party to the urban voter he has to get beyond the shire counties and districts, where activists have campaigned on a largely anti-urban, pro-Countryside agenda. The Conservatives have only one MP out of the 46 seats in the eight core cities, and fewer than half the seats in London. They also have no MPs in Glasgow, Edinburgh or Cardiff. The picture is better locally in Birmingham and in other smaller cities such as Coventry, Swindon and Southampton. Even in London a uniform swing of 5% in May from Labour would be enough to give the Tories a majority of council seats across the capital. However, the Tories have a political mountain to climb in places like Liverpool, Manchester and Newcastle.

All the main parties are converging on a cities growth agenda built around decentralisation, civic renewal and promoting urban renaissance. However, turning policy intentions into votes has proved difficult. Voter turnout in the inner cities continues to fall and may drop below 25% at the May elections. In inner London and other cities, such as Sunderland and Barnsley, continued apathy may allow the British National Party to increase its vote.

Those in the suburbs and in more prosperous city areas remain sensitive to what is happening to their city centres. None of the parties can afford to ignore suburban sentiment and demand for action to tackle urban deprivation. Suburban voters are key to electoral success in the cities. Hence Cameron's recent announcement to set up a Cities Task Force headed by Lord Heseltine, who championed the previous Conservative government's City Challenge projects. The ODPM has meanwhile set up its Shared Equity Task Force to increase home-ownership, especially for young people and key workers in urban areas. All the parties are also calling for strong city leadership, greater political diversity and democratic renewal - although ministers are wary of losing support to independent mayors like Stuart "H'Angus the Monkey" Drummond in Hartlepool.

It would be misleading to read too much into the forthcoming local elections (low turnouts, different boundaries and part-elections distort the results), but all the parties will be studying patterns of voting in the big cities. Labour can no longer take its traditional urban vote for granted any more than the Tories can rely on support from the leafy suburbs and shire counties. A new generation of city voters is emerging, who are more demanding and less forgiving. The party that can capture that new urban constituency will set the pace for future elections.