Mr Barker started his political career in 1993 and finished in 2011. He first crossed paths with Mr Horomia in the early 1990s.
"I knew him before he was an MP, when he was working with the Department of Labour. He was doing a lot of work with community groups and helping them apply for funding for a number of projects.
"He became a Member of Parliament and we shared many times on the campaign trail together."
He remembered how people gravitated towards Mr Horomia, even when they were visiting areas outside of their electorates.
"Whenever he got out of the car, he automatically drew a crowd and campaigning with him was completely different compared to anyone else I had been with. I've been to marae the length of New Zealand with him and he had an extraordinary memory in a way that he knew exactly who was on the paepae, he could identify them through whakapapa."
Mr Horomia entered his political office in 1999 under the Labour government.
He recorded the most miles travelled by a minister in one particular year, which was a reflection of the hours he'd put in for his constituents.
"He would be attending meetings, hui, tangi, than back to meetings. And it wasn't just for Ikaroa-Rawhiti, he was in Waikato, Northland the South Island, always on the move."
Working alongside Mr Horomia provided an opportunity to learn more about Maori history as well as what it takes to be "a humble person and a good person".
Mr Barker said defence of Maori interests in parliament was one of Mr Horomia's biggest career accomplishments.
"I don't think Maori could have got a better advocate."
He was also a team player and had backed Labour's controversial Foreshore and Sea Bed legislation "in very difficult circumstances".
Mr Barker said he didn't want to get into trouble with the Labour Party by suggesting who might replace Mr Horomia.
"But I think the next person to come in will be completely different because it will be next to impossible to get someone like Parekura. I could live another lifetime and I don't think I would ever meet another person like him."
Mr Horomia's body arrived at Hauiti Marae, Tolaga Bay yesterday and his funeral will be on Saturday.