Labour's national election co-ordinator, Douglas Alexander, has made a direct call for Liberal Democrats to lend their votes to Labour in marginal seats being fought over by Labour and the Conservatives.

Echoing the appeal at the beginning of the campaign by Andrew Adonis in the Independent, Alexander warns "progressive" voters who are disillusioned with the government that they would be "horrified if they woke up on 7 May and realised that their vote for the Lib Dems contributed to Cameron standing on the steps of Downing Street".

This contest "is a moment of great peril and great possibility for progressives", Alexander says. Re-electing Labour "would lead to a fundamental crisis of the Conservative Party and on the right of British politics. It would herald a new dawn for Labour and progressive politics."

But he adds, in an interview with the New Statesman: "If, however, the centre-left vote was to be split in seat after seat, we would be looking at the very real possibility of a majority Conservative government on 7 May. That is why I am determined in the final days of the campaign that we send a clear and unequivocal message that this election will be determined in large part by what happens in about a hundred Labour-Conservative marginal seats. My direct appeal to voters in constituencies across the country would be to vote for the party that can open up politics and advance an agenda for fairness. And that party is the Labour Party."

In a direct appeal to liberal-minded voters, he says: "I know that there are voters, New Statesman readers, some of them my friends, who are angry about Iraq, anxious on Afghanistan and concerned about civil liberties. But I also know that they would be horrified if they woke up on 7 May and realised that their vote for the Lib Dems contributed to Cameron standing on the steps of Downing Street."

Alexander goes on: "I believe that to maximise Labour's vote in this election and to maximise Labour's seats after this election is the surest way to defeat the Conservative Party and to herald a new dawn for Labour and progressive politics. But the risks are real and our message is clear: If you vote Clegg, you could end up with Cameron in any Labour seat on 6 May.

"It has been clear from his public comments the hostility that Nick Clegg feels towards Labour and our leader . . . so we must send a clear and unequivocal signal that the risk is real for those voters who may have doubts or concerns about Labour but are determined to avoid a Conservative government, that if they vote Liberal Democrat in those seats, they will end up with the very real risk of having delivered the keys to Downing Street to David Cameron.

"There are many who have voted Labour in the past, who face an important decision on 6 May. My clear appeal to them would be to deny the keys of Downing Street to David Cameron and to vote Labour to ensure a progressive future for Britain."

Alexander takes a further swipe at Nick Clegg, who, Labour's campaign co-ordinator claims, has "an apparent sense of entitlement" about becoming prime minister. The International Development Secretary says: "Clegg's made a big error of judgement in spending so much time in recent days talking about his own job prospects and so little time talking about the job prospects of millions of employees, workers and voters across the country.

"The economy is central to this election, and I think people are more concerned with what happens to their family and to their future than to Nick Clegg's apparent sense of entitlement."

These are excerpts from a wide-ranging interview. More extracts, on different subjects, including the TV debates and the media, will be posted on this blog. A piece on the interview appears in the next issue of the New Statesman magazine, out on Thursday.

Trancription by Ian Smith.