Gordon Brown has declared war on apathy and offered voters a "once in a generation chance" to bury the Conservatives.

In a passionate address to GMB trade unionists, Labour's campaign chief asked "the people of Britain to vote not just for a party, but for a cause".

As Millbank's concern about turning out the Labour vote grows, Brown's speech was a direct pitch to the "heartlands" that politics counts.

Outlining Labour's record in office, Brown stressed that the "journey is only beginning", telling the gathered trade unionists that "cynicism" was just another face of the Tory enemy.

"To win the battle against child and pensioner poverty and for schools and hospitals first, we must defeat not just political conservatism, but another form of conservatism - and more insidious - cynicism," he said.

The Tories, Brown argued, have given up on trying to win votes and were now trying to foster voter apathy.

"They do not even now ask people to vote for the Conservatives, nor for their leader, but simply to vote against Labour, vote against politics or not even vote at all."

Accusing William Hague of seeking to "subvert" the idea that governments can make a difference, Brown linked apathy to claims that the Tories were hostile towards public services and planning £20 billion worth of "savage" cuts.

"Their aim is to subvert the decent, progressive instincts of the British people, to defeat the very idea of a progressive public purpose and to write off, denigrate and discredit even the idea of decent public services run in the public interest," he said.

Reviving bitter memories of 80's dole queues, Brown told GMB delegates that now was the time to put the Conservatives out of business.

"At this election we ask the British people to speak out and say that public services are Britain's priority, to say clearly and unequivocally that no party which proposes to lead this country should ever again propose policies that would cut investment in education and health."

"This is a once in a generation chance to send a message that no political party can ever again win votes by undermining the NHS, our schools and our public services," he said.

Differences between the political parties count, claimed Brown, urging the people to let their vote make a difference for the vulnerable.

"If your one vote on Thursday lifts one child out of poverty, gives one young person a chance of training and a job, gives one more person suffering from pain the chance of the treatment they deserve, gives one more classroom the books and computers it needs, secures for one more pensioner a greater measure of dignity and decency in retirement, then you can be proud to have done something, not just for yourself, but for your community and your country," he said.

Sidestepping concerns over Labour's planned reforms of public services, seen by many trade unionists, including GMB members, as privatisation Brown said, "Labour's commitment is clear - investment matched by necessary reform that never loses the sight of the ethos of public service."