The family of a Birmingham lawyer killed in the 2002 Bali bombings last night described the proposed early release of 12 people involved in the atrocity as "bizarre" and said they should all serve their full sentences.

Matthew and Vivienne Arnold, brother and mother of Timothy Arnold, spoke out after it was revealed the prisoners were going to be released from jail four months early.

But Mr Arnold said he was more concerned about what was being done to bring the masterminds behind the bombings to justice.

The prisoners' sentences were reduced to mark Indonesia's Independence Day, in line with local tradition. One man who was convicted for his part in the nightclub bombing was freed yesterday.

"They are directly or indirectly involved with the bombings and should serve their full sentences," said Mr Arnold, a chartered surveyor, based in Harborne.

"It is bizarre that they are having clemency extended to them when they showed no clemency to those they took a part in killing."

Timothy's mother Vivienne added: "It just adds to the sadness."

Timothy Arnold, aged 43, had been living and working in Singapore and had been visiting Bali with his rugby team, the Bali 10s, when the bombings were carried out. A total of 202 people were killed, including 26 Britons.

The UK Bali Bombing Victims' Group said all the families who had lost loved ones in the attack were "deeply alarmed and distressed" by the news.

"It is notable that the early release of those convicted is being contemplated while key terrorists still remain either at large or yet to be brought to justice," it said in a statement.

"We wish to remind the world that the alleged bomb maker is still at large and the alleged mastermind Hambali is in American custody with no date set for his trial."

Mr Arnold said: "I'm far more concerned about getting the real people responsible for the bombings, not the people who lent out their houses to them."

The two people most strongly linked to the bomb plot are Abu Bakar Ba'asyir, the spiritual leader of the al Qaida-linked Jemaah Islamiah terror network allegedly responsible for killing, and his deputy, named Hambali.

While Ba'asyir served a 26-month sentence for the part in the atrocity which the Indonesian authorities were able to attribute to him, Hambali is being held by the United States. It means Indonesian, Australian and British authorities have been unable to question him.

"Hambali is still in US custody and he has a great deal of information that might help in capturing other people," said Mr Arnold. "He was the deputy leader of Jemaah Islamiah and has all the dirt on Bakar, but none of that can be established while he is not available for questioning.

"Four years should be plenty of time for people to try and move on. It is a long time to wait for people to be tried and that is frustrating."

The Foreign Office, criticised at the time of the bomb-ings for being slow and ill-equipped to deal with the incident, has won the appreciation of the grieving families for a memorial to the victims, which is to be unveiled in two months time.

Vivienne Arnold said it would be a "great comfort" to the families to have a solid reminder of their loved ones.