Conor Burns has resigned as a trade minister after a report found he used his position as an MP to intimidate a member of the public.
The Committee on Standards said he had broken Commons rules after suggesting he could use Parliamentary privilege over a debt dispute involving his father.
It had recommended he be suspended from Parliament for seven days.
No 10 said he would be replaced “in due course”.
Parliamentary privilege protects MPs from being sued for defamation for speeches made in Parliament.
The committee’s report found he had made “veiled threats” to use privilege to “further his family’s interests” during the financial dispute involving his father.
Apologising to the committee in March, Mr Burns said he should not have written to the member of the public “in the terms I did,” which he did using official Commons stationery.
He said he had been motivated by a desire to resolve the “long-running” dispute, which he said had a “significant” impact on his father’s health.
In February, Mr Burns had written to a member of the public connected to a company with whom his father was in dispute over the repayment of a loan.
He wrote: “I am acutely aware that my role in the public eye could well attract interest especially if I were to use parliamentary privilege to raise the case”.
The committee concluded Mr Burns had tried to intimidate the member of the public, and it was an abuse of his position as an MP which required a “sanction more severe than apology”.
It added that the dispute related purely to “private family interests” and had “no connection” with Mr Burns’s duties as a member of Parliament.