Blair dips in his pocket to give Labour's target seat campaigns £106,000

These key marginals, which Labour hopes to add to its current 258 seats, are likely to determine whether or not Ed Miliband or David Cameron wins power on May 7.

Among the local Constituency Labour Parties to have received the ex-Prime Minister's largesse are those in the SNP-held seat of Dundee East, the Lib Dem-held seats of East Dunbartonshire, Edinburgh West and Argyll and Bute and the Tories' sole seat in Scotland, Dumfriesshire, Clydesdale and Tweeddale.

South of the border the battleground seats include: North Warwickshire, its number one target, where the Tory majority is just 54; Cardiff North, which the Conservatives won with a 194 majority and Carlisle, where the Tory majority is 853.

Four out of every five of the party's target seats are Conservative-held; 88 are seats Labour lost in 2010, 15 are seats Labour last won in 2001 and three have not been held at any time between 1997 and 2010.

If Labour were to win all the target seats in addition to the 258 it currently holds, then it would have 364 seats and a Commons majority of 83.

However, holding onto its 41 seats in Scotland given the continuing poll surge the SNP is experiencing looks highly unlikely, meaning Scottish Labour's main focus is on keeping its heartland seats in cities like Glasgow.

In December, Mr Blair ruffled Labour feathers when he appeared to suggest Mr Miliband would not win the election because he had lurched the party too much to the Left.

The former party leader explained how he was "still very much New Labour and Ed would not described himself in that way," noting: "I am convinced the Labour Party succeeds best when it is in the centre ground."

Mr Blair suggested the result on May 7 could turn into an election "in which a traditional left-wing party competes with a traditional right-wing party with the traditional result". Asked if he meant a Tory win, he replied: "Yes, that is what happens."

Within 24 hours, the ex-premier tweeted that his remarks had been "mis-interpreted", stressing: "I fully support Ed and my party and expect a Labour victory in the election."

In a letter to battleground seat candidates, he says: "As the final countdown to the General Election begins, I am writing to wish you every success in your efforts to be elected and also to make a donation to your campaign.

"I know how hard it can be to raise money to fund a local campaign but for you, in one of our 106 battleground seats, it is even more vital. This is where the election will be won for Labour and that is why I am making a donation to all 106 campaigns."

Mr Blair adds: "As one of our key seat candidates you know better than most the scale of the challenge we face but I have every confidence that with your drive, determination and organisational skills, you will deliver a successful local campaign that will also see our party returned to government. So, good luck and here's to a Labour victory on May 7."

A Labour spokesman said: "We're delighted Tony Blair has given so generously to the local Labour campaigns in the battleground seats our party is targeting at this General Election.

"Our campaign is not based on big posters, talking over the heads of voters or the sound and fury of Westminster politics. It is based on millions of conversations with people on their doorsteps and in their communities."

He added: "This donation from a former leader who won three general elections for our party will help Ed Miliband win again for Labour and for Britain on May 7."

The Tories look poised to outspend Labour in the election by several millions of pounds given they began the long campaign with a larger war-chest and an array of rich donors.

Mr Cameron's party is expected to spend near the £19.5m campaign limit while Mr Miliband's hopes to raise around £12m.

Last month, Iain McNicol, Labour's General Secretary, warned party supporters as he emailed them calling for donations: "The Tories might be able buy the election."