Labour’s astonishing recent by-election defeat in Dunfermline, giving Gordon Brown a Lib-Dem MP in his own home constituency, should serve as a stark reminder that New Labour cannot presume to live for ever on the impotence of the opposition parties.

And while Tony Blair may have a checklist of reactionary measures he wants to leave behind as a “legacy” before he goes, it is clear that his back-benchers are becoming ever more edgy about the political price they and their Party may pay for supporting his marketisation of education, privatisation of health care and a right wing “law and order” agenda.

This is especially true since the election of David Cameron as a new, dynamic leader for the ageing and demoralised Conservative Party, which really does potentially create a fresh and serious challenge, at the point where Labour’s core support appears to be increasingly reluctant to vote for Blair’s policies.

The debate continues over the extent to which Cameron is genuinely wrenching the Tory party away from its Thatcherite past by setting out a new 8-point agenda which puts it level or to the left of New Labour on most social and political questions.

It is clear that many on the old fashioned right of the party are willing to let Cameron create a new, more electorally popular, “modern” and “compassionate” image for the party, while believing that if elected he would swing back to the traditional lines of policy.

In this sense Blair is seen as a model – elected on a landslide in 1997 with a mandate to sweep away the “costly and wasteful” internal market in the NHS and carry through progressive reforms, he has instead forced through market-style reforms in health and education, imposed student fees, ripped off pensioners and widened the gap between rich and poor – while politically lining up with George Bush and the neocons in costly and brutal military adventures.

Cameron’s limited progressive agenda is hedged with get-out clauses: his first point is that “a successful Britain must be able to compete with the world”, the second explicitly refutes Thatcher but still clings on to Tory notions by declaring that “There is such a thing as society, it’s just not the same thing as the state.”

The limited progressive elements in Cameron’s eight points are hard to distinguish from the politics of New Labour – but also very hard to separate from the right wing strand of the Liberal Democrats which has now won the ascendancy with the election of the 64-year old patrician Menzies Campbell as leader to take over from Charles Kennedy.

Each of the mainstream parties is now competing for a “centre” ground, wanting more private sector provision and involvement in public services, and claiming to endorse environmental concerns, and to want to “make poverty history” – while clinging doggedly to the capitalist system that thrives on widening inequality at national and international level.

And while Cameron has seen the Tories edge ahead of Labour in the opinion polls, it’s the Lib Dems that have drawn electoral blood in Dunfermline.

These two parties can stand aside from the government’s embarrassment over the Jowell affair and hope to pick up disgruntled middle class votes in the local elections in May. It is not clear whether the Lib Dem leadership result will add further impetus to Cameron: either way the dynamic is away from Blair and New Labour.

But who will offer a real opposition that will represent the interests of the working class, the poor, the ethnic minorities, the two million who marched to oppose the invasion of Iraq, the trade unions, and those fighting to keep public services public?

The logical answer should be Respect, the coalition formed out of the anti-war movement with a perspective of fulfilling precisely this role, and which has adopted a wide-ranging series of policies on many issues of domestic and international politics.

Respect has already notched up some impressive achievements, with 250,000 votes in the European elections, victories in local council elections, and of course last year’s parliamentary elections which secured not only an MP, but several impressive results elsewhere. Socialist Resistance has from the beginning been committed to building Respect.

But as we go to press the national profile and campaigning edge of Respect is falling well short of its potential, even though local organisations in a number of English cities are preparing to mount a challenge in the May elections, hoping to make further gains after last year’s triumph in securing the election of George Galloway as MP for Bethnal Green.

A press release from the Respect office correctly paid tribute to Linda Smith, the left wing comedian who tragically died last month, aged just 48: but this served to emphasise how many other issues have come and gone without any response from Respect.

The threat to close the National Coalition of Anti-Deportation Campaigns (NCADC), for example, has gone without comment: so have the forthcoming strikes by University lecturers, and the ballot for strikes to defend pension rights of 2 million local government workers.

If Respect is to strengthen its initial implantation in the trade unions and move towards a perspective of winning affiliations from major unions such as the RMT then a more systematic attention to trade union concerns is essential.

It is a worrying fact that the organisation has no systematic arrangement to issue press statements on most of the main developments in British politics: indeed it has only the most rudimentary publicity machinery at national level.

And despite a membership embracing campaigners at the forefront of issues such as education policy, defending council housing, defence of refugees and asylum seekers, and a host of other pressing issues, Respect has not managed to project a national profile that reflects this strength.

Local campaigning is indispensable, but this would be strengthened and in every way by an enhanced national profile, in which the organisation puts itself forward as a reference point for comment and analysis on the political agenda of the day.

The decision from last November’s conference to establish specialist policy working parties that will feed more developed research and information to Respect national leaders and local candidates needs to be put into practice.

Respect cannot assume that demoralised voters from New Labour will simply gravitate to its local candidates on May 4: having seen the moral and political collapse of the main party which was seen as representing the working class, they need convincing to go out and vote for a left alternative.