Tony Blair has donated £1,000 to the local campaigns in each of Labour’s 106 key target seats, telling candidates he is giving the money because he knows these are the seats where the campaign will be won or lost.

In a letter to candidates, Blair wrote that he wished them every success. The former prime minister has made a series of ambivalently phrased statements about the scale of his support for Ed Miliband and in his brief letter to candidates he made no direct reference to Miliband or the policies he has developed to ensure a victory.

He wrote: “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.

“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.”

A Labour spokesperson said Blair would be involved in the campaign, adding: “We’re delighted that Tony Blair has given so generously to the local 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.”

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His remarks came as Miliband, in an interview with Progress magazine, often described as a Blairite journal, said one of the proudest achievements of his leadership was to maintain a pro-European stance.

He predicted that, if elected, the Tories would fall into chaos over Europe and even some Tory MPs would consider defection.

He told Progress: “I think it’s a real sign of the party’s maturity actually that 30 years ago we were the party of the antis, and now it’s the Tories who are drifting towards exit … There are lots of dangers of a Tory government, but one of them is: Where are they taking us on Europe?”

He predicted a Labour victory would lead to turmoil inside the Tory party as arguments break out between Boris Johnson, the mayor of London, and Theresa May, the home secretary.

“Goodness knows what will happen to the Tories with an election defeat,” Miliband said, adding “there is a moment coming in the Tory party, because there are probably more [Tory members of parliament and supporters] that are pro-European who have kept quiet, and there will be a big question about which direction they go in”.

He said: “I want as many people as possible backing us … There are many pro-Europeans who will be very alarmed at the direction of travel within the Tory party. There are many people who believe in One Nation who [will] think, ‘Where is the Conservative party going?’ So I’ll take as many supporters as possible.”