I am worried that Jacqui Smith may be losing her identity. Does she know that she is the Home Secretary? Does she realise that, since the identities of 25 million people were lost in the post, there are a few tiny doubts about whether the Government can run a national ID card scheme (or, indeed, a bath)? Does she know that it is her job to make us think that she is competent?

The topic of identity dominated Home Office Questions. The first time the subject came up, a Tory shouted: “They’ve lost it.” No one on the front bench laughed. I wonder why.

Ms Smith had many inquisitors. The first was the senior Labour MP Keith Vaz, who is deeply oily but that makes it all the more slippery when he asks a good question. After the events of last week, he demanded, was she planning to look again at how to protect ID scheme data. As his words oozed over us, like treacle over sponge, Ms Smith just sat there. She did not jump up, eager to inform. Instead she looked over at her Immigration Minister, Liam Byrne. He popped up and trumpeted: “The House will know that, where there are lessons to be learnt from last week’s events at HMRC, then it is right that we learn them.”

This was clearly nonsense. Ms Smith nodded away earnestly. Why? Could this really be the Home Secretary? Was she in charge? Perhaps we should check her biometric data just to make sure. David Davis, the Shadow Home Secretary, knows exactly who he is. He is her tormentor. He can smell weakness but he asked a simple enough question. “If the Government gives away your bank account details, that is a disaster but you can change your bank account,” he noted. “What precisely do you do if the Government gives away your biometric details?”

Here was another chance for Ms Smith to tell us of her strategy or, at least, to pretend to have one. Instead she said: “Biometrics will link a person securely and reliably to his or her unique identity.”

No one looked reassured. I cannot think why: surely the news that our biometrics can link us to ourselves can only be good, but Ms Smith, or her impostor, struggled on, to loud barks of laughter. “The current plan for the national identity register is that biometric information would be held separately from biographical information, thereby safeguarding against the sort of eventuality that you are talking about.”

Mr Davis, looking like a shark who had just had a tasty snack, asked her about a European information-sharing scheme called Project Stork. “How are we going to prevent a repetition of the disaster of the last few weeks when sensitive personal data is held not by one government but by 27?” Ms Smith looked flummoxed. I don’t think she knew about Project Stork. Again, this was worrying. Wouldn’t a real Home Secretary have a clue about this?

Doubts grew in the chamber about her true identity. Even Nick Clegg, the Lib Dem leadership candidate and sometime MP, looked puzzled but Mr Clegg is an expert on changing identities. He used to be the Lib Dem poster boy, now he is Calamity Clegg.

I could see him, and others, eyeing Ms Smith with alarm. Fears grew that she was a victim of a similar process. We have all heard of Calamity Jane. Perhaps she had now become Calamity Jacqui.

We need to check her fingerprints as soon as possible.

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