Three former Pakistan international cricketers were escorted from the dock by prison officers on Thursday after being handed combined jail sentences totalling four years for their part in the spot-fixing plot in their Test match against England at Lord's last year.

Salman Butt, the Pakistan captain during that Test and a man described by Mr Justice Cooke as "the orchestrator of this activity", was jailed for 30 months.

Mohammad Asif, who bowled one of three prearranged no-balls at the centre of the conspiracy, was given a year in prison. Mohammad Amir, who at the time of his crime was only 18 years old, was given a six-month sentence. They must serve half of their sentences before release on licence, and must do so in English prisons.

It is a heavy price to pay for three men who, as the judge recognised, had until last year been "heroes" for their nation and icons in their sport.

"The [essence] of the offences committed by all four of you is the corruption in which you engaged was in a pastime the very name of which used to be associated with fair dealing on the sporting field," said the judge. "'It's not cricket' was an adage."

Butt's agent, Mazher Majeed, was described by the judge as being equal to Butt as one of two "architects of the fixing", and was given a 32-month sentence, the heaviest handed down in courtroom four of Southwark crown court on Thursday. The judge softened what would have been a four-year sentence for Majeed in recognition of his guilty plea.

Amir, who will be sent to a young offenders' institution to serve his punishment, also pleaded guilty, reducing his sentence from nine to six months.

Although Butt had falsely protested his innocence throughout, his ban from all forms of cricket issued by its world governing body – and extending for at least five years – led the judge to reduce his custodial sentence by 18 months. The two bowlers are serving similar minimum five-year bans from the International Cricket Council. "That is the punishment imposed by the cricket authorities," said the judge, "but these crimes of which you have been convicted require that a sentence be imposed which marks them for what they are and acts as a deterrent for any future cricketers who may be tempted.

"These offences, regardless of pleas, are so serious that only a sentence of imprisonment will suffice to mark the nature of the crimes and to deter any other cricketer, agent or anyone else who considers corrupt activity of this kind, with its hugely detrimental impact on the lives of many who look to find good honest entertainment and good-hearted enjoyment from following an honest, albeit professional sport."

Though some might consider innocuous the deliberate bowling of no-balls at a cricket match, since it leads only to a team conceding one single run to the opposition's tally, the judge set out his motivation in clear terms. The impact reaches far beyond the figures inscribed on a Test-match scorebook and debases the credibility of the entire sport.

"Now, whenever people look back on a surprising event in a game or a surprising result or whenever in the future there are surprising events or results," said the judge, "followers of the game who have paid good money to watch it live or to watch it on TV will be led to wonder whether there has been a fix and whether what they have been watching is a genuine contest between bat and ball. What ought to be honest sporting competition may not be such at all."

Mr Justice Cooke also made plain his concern that the four men's activity set out "to defraud bookmakers." The fact that the charges against them resulted from a News of the World sting did not impact heavily on the sentences issued, since the court heard evidence that Butt, Majeed and Amir were all "discussing such activities outside the scope of the sting".

Depressingly for cricket, the judge gave a hint of his belief that the four men's crimes were probably not isolated but could have been "the tip of the iceberg" and "part of the common culture."

Indeed, the judge held up to Butt the mirror of his own description of his crimes. "In the words you used to the jury – what you did was 'a terrible thing – it is bad for the game of cricket, bad for the country and shows the character of the man involved'," Mr Justice Cooke said. "Those were your own words."

Pakistan spot-fixing: the judge's full verdict