Home Secretary Jacqui Smith has refused to apologise to MP Damian Green over his arrest in connection with a series of leaks from the Home Office.

Ms Smith was asked on the BBC’s Andrew Marr Show on Sunday whether she felt she should apologise for the way the shadow immigration minister was treated.

But she sidestepped the question and insisted the way in which his arrest had been carried out was an operational matter for the police.

Mr Green was detained for nine hours and extensive searches of his home in London and Kent, as well as his constituency office, were carried out by Special Branch officers.

There has been rising indignation about the arrest across the political spectrum as further details have emerged about how nine Special Branch officers searched through personal belongings at the shadow immigration minister’s London home on Thursday.

Ms Smith said: "Any police investigation that involves an investigation of a senior politician or elected member is highly sensitive and decisions need to be taken very carefully about it. It is not an investigation about whether opposition politicians use information to embarrass the Government. That is a completely legitimate activity."

She said it was for police to decide how to "follow the evidence where it leads them".

During the interview, she denied knowing in advance Mr Green, who has emphatically denied any wrong-doing, was to be arrested. "I was told about the search and arrest after it happened."

Pressed again about why she was not apologising, the Home Secretary said: "If you believe that the professional judgement of police officers should be able to take its course, then you believe that regardless of whether it is tricky or difficult."

Former Conservative party leader and Folkestone and Hythe MP Michael Howard, meanwhile, has added his voice to those criticising his colleague’s arrest.

Mr Howard said: "I think it is completely outrageous. It is outrageous because you can’t have one rule for Gordon Brown, who when he was in opposition built a career around leaks and different rules for somebody else.

"If it was OK for him, it should be OK for everyone else. It is very important for a vigourous and healthy democracy that politicians are held to account and exposed to scrutiny about what they are doing and have done."

There was a "huge difference" between Mr Green’s arrest and the investigation and arrest of Tony Blair in connection with the cash for honours affair, he added.

Mr Green was exposing matters that were in the public interest, he said.