Mr Fitzpatrick, currently a junior transport minister, was a leading member of the Fire Brigades Union and a former Government Whip.
Originally from Scotland but based in London, Mr Fitzpatrick’s special interests include environmental and animal welfare issues.
He is also a member of Greenpeace.
Mr Fatzpatrick’s anticipated move to DEFRA comes after Jane Kennedy handed in her resignation over Gordon Brown’s leadership.
Ms Kennedy said she stepped down from the post as she was unable to give assurances that she supported the Prime Minister.
Following a “frank and honest discussion” with Mr Brown, Ms Kennedy said she did not believe he was the right man to lead the Labour Party into the next election.
Mr Brown should indicate he had listened to voters and step aside, she said.
Ms Kennedy took the DEFRA last October in a reshuffle after Jeff Rooker stepped down as food and farming minister.
She was the seventh minister to leave the government in the past few days amid poor local and European election results.