John Prescott is facing questions about his son's business dealings amid claims that he was cashing in on his father's house-building plans.
The Sunday Times said Johnathan Prescott's regeneration company, Estate Partnerships, was identifying land for property firms that would increase in value with planning permission.
There is no suggestion that the Deputy Prime Minister's son has done anything illegal.
But shadow Communities and Local Government Minister, and Midland MP, Caroline Spelman said she would be tabling a series of parliamentary questions about the issue.
Mr Prescott was responsible for planning decisions in England and Wales until May 5, when he was stripped of his department in Prime Minister Tony Blair's reshuffle.
In particular, he was reportedly involved in the planning process for Eaglescliffe Logistics Centre, a commercial site in Middlesbrough in which his son's company was also involved.
Ms Spelman (Meriden) said: "This matter is very serious, and there is going to be outrage if there is any evidence of a conflict of interest."
A spokesperson for Mr Prescott said: "The Deputy Prime Minister has always abided by the ministerial code and the guidance on propriety issues for handling planning casework."
Mr Prescott's son told The Sunday Times: "I keep my business very clean and my dad doesn't know anything - we never speak about my business. I don't tout my name."