Former Stafford Hospital boss Martin Yeates could avoid appearing at the public inquiry after its chairman announced new rules on written evidence.

Campaigners have attacked the move which could allow Mr Yeates to submit written evidence to the inquiry rather than attending as a witness and giving evidence on oath.

Robert Francis QC, who is leading the investigation into failures at the hospital, revealed yesterday changes to the protocol on how written evidence will be used by the inquiry.

Although Mr Francis did not mention Mr Yeates’, the changes could make it possible for the former boss to submit a statement instead of appearing in person.

Making his announcement Mr Francis said a written statement read out during the public hearings should be treated as evidence in the same way as if the witness was called to give testimony.

But he said the fact the evidence would be given unchallenged did not mean it would be treated as accurate. He said: “The weight to be attached to that evidence remains a matter for me, the chairman, taking into account all relevant matters.

“Where a statement is read into the record because the witness who would otherwise have been required to give evidence in person and would have been subject to challenge is unable to attend to give oral evidence through illness or some other reason accepted by me, I will have particular regard to the fact that the evidence could not be challenged in person when considering the weight to be attached to it.”

Lawyers acting for Mr Yeates have claimed the former boss, who has never spoken publicly about his time as head of the trust, is mentally unwell.

Mr Francis said lawyers taking part in the inquiry would have 14 days to challenge any written evidence.

Julie Bailey, founder of campaign group Cure the NHS, said: “It is ridiculous that we can have a public inquiry into failings at Mid Staffs and the chief executive, it would appear, is not going to be giving evidence because he is apparently ill.

“Getting a written statement is better than nothing but we wanted him to stand there and be challenged as to why our loved ones died in that hospital.”