Chaytor must "learn to be anonymous" - Jonathan Aitken

Mr Aitken, who was jailed for 18 months for perjury and perverting the course of justice in 1999, warned his fellow former MP that his first few hours and days behind bars will be difficult.

But he added life inside will not be dangerous for the politician, saying he will be treated as ''just another ordinary prisoner'' if he can keep his head down.

Mr Aitken, who spent seven months behind bars, said: "All men are equal in a prison uniform so he will need to forget quickly that he was once someone who was important.

"I don't think there will be the slightest preferential treatment for him, but nor will there be any unpleasant treatment for him.

"He will be just another ordinary prisoner, as I was, and that's the best thing that will happen to him. The more anonymous he can be and the quieter it can be for him, the better."

Mr Aitken, 68, said a jail sentence would be a shock for anybody and warned that Chaytor "will find his first few hours and days in prison difficult".

"But he will also find - if his attitude is right and if he avoids being a tall poppy and goes with the flow of prison life - that it's a life he can cope with.

"Prisons on the whole are run by good prison staff so he doesn't need to be full of fear about lurid stories about beatings up and so on.

"Prison will not be a pleasant experience for him but it won't be an impossible experience either."

Mr Aitken, who was chairman of a high-powered group of criminal justice experts that examined the state of Britain's prisons in 2007, went on: "Prison is a good place to reconcile where one went wrong in life and how one might start again in a different rehabilitated life.

"I have every confidence he will cope. The experience will be difficult but not one which will be dangerous or particularly nasty.

"He will be another average prisoner who will go with the flow of the prison."