Johnson quit as shadow chancellor in 2010 and has been on the backbenches ever since.
Blunkett said: "My own feeling is that there is lots of room for Alan Johnson being given a role. I understand entirely the need for a new energised generation to be given their chance. I hope that might include at least one 'oldie' in the guise of Alan Johnson, who has a terrific contribution to make".
Blunkett also disclosed he would have given serious consideration to taking a Ken Clarke style role in a Miliband government if offered one, and said he agonised over the decision to stand down – a decision he disclosed to his Sheffield constituency Labour party on Friday.
Asked whether he would have rethought his own decision to retire if Miliband had offered him a post, Blunkett said: "I would have given it serious consideration since I came into politics to make a difference and be where decisions are taken. That is what I loved doing in the 90s in the cabinet and you can only do that from the inside."
He admitted: "I agonised over resigning. It's been quite traumatic. It's done now. There is no going back. I have got on with it now. I have got to get used to not being in the public eye and hold back now and learn to be a human being. It's going to be difficult but you have to remember if you are elected you do have a mandate."
He also revealed his two biggest political regrets. First, he said he should not have tried to introduce "an all singing and dancing identity card", but instead introduced a requirement to own a passport, something more than 80% of the population already had. He said the change would have not generated the same fears, but allowed a government to control migration.
Second, he said he regretted not doing more to fight for funding of measures to increase integration of different ethnic communities.
With some frontbenchers privately questioning the abilities of Miliband, Blunkett warned his party not to get distracted by tittle-tattle and to recognise that if Labour lost, the Tories would redraw the map of politics to make it near insurmountable for Labour to win in future.
He said: "If we don't win we are out in the wilderness for a long time. A Tory majority government would bring in radical boundary changes that would give them 30 extra seats. They would with the help of the Liberals – because the Scottish secretary Alistair Carmichael is on the record in the past week saying this – take away the right of Scottish and Welsh Westminster MPs to vote on health, education and other issues that would be devolved to their parliaments. They would change party funding and they would stuff every public service agency and every public quango with their own people – which they have already started. Winning in May 2015 is absolutely imperative and everyone should stop tittle-tattling and recognise they just have to get on with it and win."
Blunkett, both as home secretary and education secretary, was at the centre of the nexus of the most difficult issues of immigration, integration and a response to globalisation – the issues that have led to the rise of Ukip and the widespread alienation from politics. He admitted that the political class, including the Blair government, struggled to find answers to the impact of globalisation.
He argued: "We have to accept that free movement of workers in the EU is here to stay. 'Auf Wiedershen Pet' was our workers going one way, and now we have workers seeking jobs here. We can be honest with people and say within the bounds of free movement, it is better to have people work openly and legitimately pay tax and national insurance than working in the black economy, but we should be tough as boots on earned entitlement and conditionality. That really means getting a grip on access to services and benefits until migrants have earned it – that is perfectly logical and about mutuality and reciprocity. We can justify that as part of our values and present it to the disaffected and the alienated as a clear and potentially achievable set of goals. The government's target of a net reduction in immigration is a nonsense because it is entirely dependent on how many people leave and that is something government cannot control."
He said: "If I was pleading guilty, it was to failure to fight for enough resource for integration policy. We should have said we will concentrate on that and will invest sensibly in measures that help communities to survive these changes, so they feel someone is on their side. The migrant impact fund was never large enough and was then abolished altogether in 2010 by the coalition."
He then admitted to a larger and more surprising error: "If I had my time again, instead of going for ID cards I should have gone for every adult citizen having a passport. We already had 82% possession of a passport, the highest density in the world. If we had done that, we would have got a clean register based on properly authenticated passport applications so people could have been issued with an easy to issue card to go with it.
"That way we would have taken the steam out of it. People are quite happy to offer details for a passport application, but they were manoeuvred into being fearful of an identity card. A passport requirement would have been a way of checking entitlement to benefit, to help and education. Employers would have been required to check whether people were entitled to work. It might have taken longer, but it would have allowed us to have embarkation controls that at the moment the government cannot implement.
"That would have been a simple way to deal with it, so, on reflection, it was a mistake to try and go for an all singing and dancing alternative rather than building on what we had. We would have got it there in the end."
More broadly, he argued that the political class did not know how to respond to the financial crash. "I think they were not quick enough before 2010. We did not have a narrative. We did not have an explanation for what was happening on a global scale. Politics itself was struggling to find answers to it. Ironically Gordon [Brown] was leading internationally in trying to find those answers. He won enormous accolades in April 2009 from Christine Lagarde and Obama and others in 2009, but then none of that carried forward into the following year, partly due to the expenses scandal that derailed any kind of hearing people were prepared to give us about what was happening globally."
Despite his own personal travails played out in public – including his resignation as home secretary, the exposure of his affair with the Spectator publisher Kimberly Quinn and his painful battle to retain contact with his son William – he insisted he was not bitter with the journalists that brought him down.
"I don't hold grudges, it just corrodes you inside. The one thing I do feel is that some journalists that ought to have known better did not realise the extent to which personal issues were played into the public arena." One suspects he feels the story about the visa for Quinn's nanny was less about Home Office procedures than the battle raging in the family court over his son.
He added: "They want us politicians to have a conscience and, by God, I've got a conscience. I've taken responsibility for all my actions, private and public, all my life and I'm still carrying that now and I'm pleased to do so."
He ended by saying: "The strength of democracy is the link between the individual and a defined geographical community. We break that at our peril. The best way to restore trust and confidence in politics is for people to be rooted in a constituency and to be in touch with the feeling of pain in their constituency, and then to reflect as best they can. In a rapidly changing world culturally and economically, all sorts of subliminal fears emerged. People were not sure globalisation was benign and since 2007 it has not been benign and that is why austerity has bitten in personal terms and into their perception of politics and who is really on their side. People have got be helped through this period of rapid and painful change and they have to be given answers that give them hope. If there is one word that is critical in the next months, it is hope and for Labour to convey it."
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