Nasrullah Jan Khattak told the BBC he was confident his 23-year-old son, Abid Naseer, would get justice from the British legal system.
Police are questioning 11 men arrested during raids in Manchester, Liverpool and Lancashire.
Most of them are Pakistani nationals in the UK on student visas.
Mr Khattak told the BBC that no-one in the family had ever had links with any extremist groups.
"I'm astonished how they could think that Abid has links with militant or terrorist [groups]," he said.
"We are never involved in such activities.
"We cannot think about that - only education and prayers and fasting and that's it. We are never involved. Not political, not active with anybody, not militant.
Nasrullah Jan Khattak
Last Friday evening, officers were granted an extra week to question the 11 men - aged 22 to 41 - arrested on suspicion of plotting to detonate a bomb in north-west England.
An 18-year-old man released into the custody of the UK Border Agency will be deported, the BBC understands.
Mr Khattak said his son had appreciated the "freedom and respect of humanity" during his two years in England and that he had seen no change in him during that time.
His own experience of working with British people in Saudi Arabia and hearing about their homeland had given him faith in the UK legal system to treat his son fairly, he said.
"That they will do justice, I have heard from my son. And I related this, if they do injustice I will be shocked for that," he said.
Members of the North West counter terrorism unit raided at least 14 properties in Liverpool, the Cheetham Hill area of Manchester, and in Clitheroe, Lancashire, last Wednesday.
Greater Manchester Police said that on Tuesday afternoon, searches were continuing at four homes in Manchester and five in Liverpool.
Police say they have not found any explosives or identified a clear target for the alleged bomb plot.
However, the BBC understands that images of the popular Arndale and Trafford Centre shopping complexes, Birdcage nightclub and St Ann's Square, all in Manchester, were found during searches.
On Monday evening, army bomb disposal officers were called in to one of the homes being searched in the Wavertree area of Liverpool as a "precaution". They have now been stood down, although the police search continues.
-----------------------------------------------------------
N A D E E M M A L I K
Director Programme
AAJ TV
ISLAMABAD
00-92-321-5117511
nadeem.malik@hotmail.com
See all the ways you can stay connected to friends and family
