Conservative MP Jacob Rees-Mogg has said he "clearly made a mistake" when he spoke at a dinner held by a right-wing group in May.
Mr Rees-Mogg was guest of honour at the Traditional Britain Group's annual dinner in May.
The group's Facebook page calls for Doreen Lawrence, the mother of murdered black teenager Stephen Lawrence, and "millions of others" to be "requested to return to their natural homelands".
TBG denies being a far-right group.
It says it supports leaving the European Union and halting immigration but should not be "smeared".
Posts by the group on its Facebook page criticised the decision, announced last week, to make Mrs Lawrence, whose son was murdered in a racially motivated attack in 1993, a Labour peer.
It is also critical of the Conservative Party - saying its current leadership is "liberal left" - and "likes" the Facebook page of far-right French politician Marine Le Pen. It praised a by-election victory by her National Front party in May as "excellent".
Mr Rees-Mogg, MP for North East Somerset, addressed the group at their function in London in May.
In a statement, he said he had been warned the day before about the group's "right-wing connections" and had questioned the organiser about them, who had told him "it was a smear".
"I am shocked by the comments made by members of the Traditional Britain Group which I note from the Liberal Conspiracy website seem to have been made after I had addressed the dinner," Mr Rees-Mogg said.
"I can entirely disassociate myself with the Traditional Britain Group as I have never been a member or supporter."
He later told BBC's Newsnight: "I clearly made a mistake. I think the postings that we've recently seen are so deeply disgraceful and shocking that they have no place in decent political debate.
"Mrs Lawrence is a wonderful and courageous woman who has contributed to British public life and, in any traditional view of Conservatism, she should be lauded for what she has done."
Mr Rees-Mogg added: "I clearly didn't do enough work to look into what they [the TBG] believed in."
But Gregory Lauder-Frost, the group's vice-president, told the BBC that it had "no links with any far-right organisations" - although it took an interest in "some overseas political parties" that "the BBC and other media outlets" described as such.
He said: "The TBG also is concerned with an entire range of issues. But we believe that exiting the EU and halting immigration are crucial to the survival of the British nation.
"One appreciates this upsets the liberal-left but we should be permitted to entertain our own opinions on these matters just as they are, without being smeared as 'far-right'. It is clear that people across the political spectrums amongst the man-in-the-street are concerned about immigration."
He added that the group was "a traditional conservative organisation concerned about the future of Britain and our nation" which encouraged discussion on its Facebook page by "sometimes provocative links to stories".
It later emerged that Mr Lauder-Frost is also a member of UKIP.
A UKIP spokesman said: "Mr Lauder Frost is an ordinary member, he holds no position or authority in the party. The Trad Brit Group is not proscribed by the party, so no action can be taken."
Labour MP Sheila Gilmore said it had been a "serious error of judgement" by Mr Rees-Mogg and said he should make it clear that he did not support the views expressed on the group's Facebook page.