Liam Fox said he resigned from his job as defence secretary "without bitterness or rancour" as he apologised to the House of Commons for breaching the ministerial code.
Dr Fox said he had been "overwhelmed" by the support he had received from colleagues as he made a five-minute statement in the chamber.
He said he accepted the conclusions of Cabinet Secretary Sir Gus O'Donnell's report into his relationship with self-styled special adviser Adam Werritty.
But he criticised sections of the media for running a vindictive campaign, adding that elderly members of his family had been harassed.
Dr Fox said: "I have attempted to be clear and transparent on all the issues raised. I would like to say again that I am very sorry to all my colleagues here in the House and to all those who feel let down by the decisions that I have made.
"I have always believed in personal responsibility and I accept the Cabinet Secretary's conclusions. I am pleased at the explicit acknowledgement that I neither sought, expected, nor received any financial gain that was being widely and wrongly implied.
"I also welcome the clarification of the fact that no national security issues were breached, no classified documents made available, and no classified matters briefed. These accusations were also widely made and deeply hurtful.
"The ministerial code had been found to be breached and for this I am sorry. I accept that it is not only the substance but perception that matters and that is why I chose to resign. I accept the consequences for me without bitterness or rancour.
"I do not blame anyone else but I believe you do not turn your back on your friends or family in times of trouble."
Dr Fox's wife Jesme Baird watched her husband give his statement from the seating area reserved for VIP guests in the public gallery.
There were loud cheers from the Tory benches as Dr Fox arrived at 1.48pm. He was flanked on the backbenches by Dan Byles, John Glen, whip James Dudderidge and senior Tory Oliver Heald.
He had to wait for Commons leader Sir George Young to finish answering questions from MPs about Sir Gus's report before he began reading his prepared statement to the Commons.
Dr Fox began his statement by describing a visit to the Libyan city of Misrata two weeks ago where a man showed him pictures of his dead children.
"A few days later I resigned from the Cabinet," Dr Fox said. "One was an unbearable human tragedy, the other was a deep personal disappointment. I begin with that necessary sense of proportion."
He went on: "As I said in the House last week, I accept that it was a mistake for distinctions to be blurred between my professional responsibilities and my personal loyalty to a friend.
"I accepted then it was a mistake to attend a meeting with a potential supplier without an official present and, with hindsight, I should have been more willing to listen to those around me."
Dr Fox then lashed out at sections of the media who had "hounded" his relatives as they sought to uncover information about his dealings with Mr Werritty. He said that many were elderly or children, and he claimed that the behaviour of some journalists was "unacceptable".
He also claimed the media should not have been so ready to take the word of Harvey Boulter, the private equity boss who the former defence secretary met for dinner with Mr Werritty in Dubai.
Dr Fox added: "I believe from some quarters that there was a personal vindictiveness, even hatred, that should worry all of us."
He went on to thank his constituents and fellow MPs for their support, as well as the Ministry of Defence's civilian staff and senior military personnel.
Home Secretary Theresa May and Communities Secretary Eric Pickles were on the front bench to hear Dr Fox read his statement.