Shadow home secretary Diane Abbott has said she no longer opposed the security services as she insisted her time as a graduate civil servant would prepare her for becoming home secretary.
Ms Abbott also tried to distance herself from claims she supported the IRA in the 1980s, saying: "I don't have the same hairstyle, I don't have the same views."
It came as Labour pledged to recruit 1,000 more staff at security and intelligence agencies MI5, MI6 and GCHQ to step up efforts to prevent terrorism.
Ms Abbott was challenged on her views after it emerged she had signed a parliamentary motion calling for an end to "conspiratorial groups" in 1989.
She told the BBC's Andrew Marr Show: "At that time, I and a lot of people felt MI5 needed reforming.
"It has since been reformed and of course I would not call for its abolition now."
Pressed on the issue, she said: "That MI5 has gone. It's been reformed, it's a different MI5 and that's why so many of us are able to support it now."
She defended voting against "counter-productive" counter terror legislation, which was also opposed by many senior Conservatives.
Asked about her views on the IRA in the 1980s, she said: "It was 34 years ago, I had a rather splendid afro at the time. I don't have the same hairstyle, I don't have the same views.
"It was 34 years on. The hairstyle is gone, some of the views are gone."
Ms Abbott insisted that she had worked as a graduate trainee in the Home Office so she was qualified to take on the role, which would make her the first black person to hold one of the most senior ministerial positions.
She said: "First of all, I think there's something to be said for a home secretary who has actually worked in the Home Office.
"I worked in the Home Office for nearly three years as a graduate trainee and I know how it works from the inside."
Ms Abbott, who has represented Hackney North for 30 years, said her experience working in diverse communities would help her in the role.
Home Secretary Amber Rudd shot back at Ms Abbott's comments, telling the Andrew Marr Show: "What I would say to Diane Abbott is I have changed my hairstyle a few times in 34 years as well, but I have not changed my view about how we keep the British public safe."