Mr Seymour said he had bought ****27 million ***** Trinity shares between November and February at an average price of 22c per share.
The Seymour Group had sold 25 million shares over the past two days and would aim to offload the remaining 2 million shares today.
Mr Seymour said Trinity, which is at the heart of the "Labor mates" scandal, was "poorly managed" and "no longer worthy of further investment".
He also attacked the group's "questionable transactions", referring to a secret $1m payment it made to Ross Daley, the then general manager of powerful Queensland lobby group Enhance Corporation.
"It defies logic and is not good business practice to pay fees to lobbyists privately and yet fail to disclose the amount and reasons for the payment," Mr Seymour said.
Last Friday, after that deal was revealed by The Australian, superannuation funds whose cash Trinity had invested demanded that Trinity be removed as fund manager.
Trinity said its "independent advisory board" had voted to remove Trinity as the manager of $800m worth of unlisted property trusts.
Since then, shares in Trinity have halved from 14.5c to 7.3c as investors, including Mr Seymour, dashed to the exits. Funds management is a major source of the group's revenue.
"The income from the remaining business would be minimal when compared with the costs involved in managing what is left of a public company," Mr Seymour said yesterday.
Trinity chief executive Craig Bellamy said Mr Seymour's decision to sell his stake in the company was disappointing but said Trinity had a "robust model" and a "team of highly skilled staff".
"Trinity is currently rebuilding its executive management team and board and is extremely focused on renewal at all levels," Mr Bellamy said.
"We cannot be distracted by day-to-day investor movements; we must remain focused on our key priorities.
"We acknowledge these are challenging times but rest assured we are taking decisive action and addressing governance concerns."
Mr Bellamy said Trinity would "vigorously pursue" its right to manage its unlisted managed funds and would apply to do so through an expected public tender process.
Following revelations of the controversial $1m payment to Mr Daley, Trinity announced it had appointed Deloitte to investigate the transaction.
Trinity has said it will not decide whether to release that report until it knows what it contains.
Queensland Premier Anna Bligh yesterday called for the Crime and Misconduct Commission to investigate the latest South-east Queensland Regional Plan, but continued to reject calls for a royal commission.
The investigation comes amid the Labor mates scandal, with concerns that former Labor MPs, working as lobbyists for developers, could have influenced some of the decision-making processes behind the plan.
Mr Seymour said he had bought 27 million Trinity shares between November and February at an average price of 22c per share.
The Seymour Group had sold 25 million shares over the past two days and would aim to offload the remaining 2 million shares today.
TCQ Price at posting:
7.3¢ Sentiment: LT Buy Disclosure: Held