Ministers were facing a political storm today after a convicted Islamic terrorist was released early from jail under a scheme to ease prison overcrowding.

Yassin Nassari from Ealing was jailed for three and a half years last July after he was caught with a blueprint detailing how to make a missile and explosives for its warhead.

But it emerged today that the 28- year- old Londoner was secretly freed from Wakefield Prison last month after serving less than half his sentence.

The Ministry of Justice had failed to disclose its decision, but was forced to rush out a statement confirming Nassari's release after being confronted by a Sunday Times journalist.

Today's revelation is certain to prompt fresh concern over the early release scheme, which was introduced last year to ease record prison overcrowding. It allows "non-violent" prisoners to be freed up to 18 days early.

Nassari would have been eligible for automatic release after serving half of his sentence, backdated to when he was first taken into custody, but the date was brought forward under the early release scheme.

Shadow justice secretary Nick Herbert said: "It is disgraceful that a convicted terrorist has been released before even half of his sentence has been completed.

"While the Government is seeking to extend the period of pre-charge detention without charge, never mind conviction, at the same time they are releasing convicted terrorists early. The early release scheme should be scrapped immediately."

The decision to release Nassari comes despite the gravity of his offence and unconfirmed reports last year that he had been moved from London's Belmarsh prison because of fears that he was planning to blow up the jail.

Further evidence of the potential threat posed by Nassari was revealed at his Old Bailey trial last year, at which he was convicted of possessing material likely to be useful to a terrorist.

As well as the missile blueprint, which set out how to build an Al-Qassam rocket of the type fired into Israel by Palestinians, the court also heard how Nassari had shared extremist videos with another terrorist containing information about suicide vests, booby traps, poisons and car bombs.

A letter from his wife, Bouchra el-Hor, urged him to wage jihad and said she hoped their fiveyearold son would become a martyr.

In its statement today, the Ministry of Justice said that although terrorist convicts jailed for offences involving "serious violence" were not eligible for early release, the nature of Nassari's crime meant that he was not covered by this prohibition.

A spokesman added: "A category A prisoner was released from Wakefield prison on 11 February 2008. The prisoner met the criteria for early release under the End of Custody Licence scheme. Where a prisoner satisfies the criteria then release must follow.

"ECL is only available to prisoners whose offences are not considered serious enough by the court to justify a long term of imprisonment."

Nearly 19,000 offenders have been freed ahead of time since the start of the Government's early release scheme including more than 3,500 violent offenders. At least one criminal has committed murder after being let out early.

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