The International Bar Association's Human Rights Institute (IBAHRI) said Sri Lanka had granted its members visas in August but revoked them last month.
However, a statement from the Sri Lankan government said the claim was a gross misrepresentation of facts and an attempt to sully the image of the country.
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The IBAHRI delegation included United Nations Special Rapporteur on the Independence of Judges and Lawyers Gabriela Knaul, and the first UN Special Rapporteur on the Independence of Judges and Lawyers Param Cumaraswamy, IBAHRI said in a statement.
According to the organisation, Sri Lanka's Ministry of External Affairs told it on October 30 that they did not want the conference to go ahead and the visas of the delegates would be revoked on arrival at the airport.
The Conference titled 'Making Commonwealth Values a Reality: the Rule of Law and the Independence of the Legal Profession' was scheduled to take place on 13 November, ahead of the three-day Commonwealth Heads of Government Meeting (CHOGM) set to start here on November 14.
IBAHRI said that the latest denial was the second incident of visa refusal by Sri Lankan authorities. The association has been critical of Sri Lanka's impeachment of lady Chief Justice Shirani Bandaranayake in January.
She was dismissed on grounds of misconduct, which she described as a political witch hunt for her refusal to toe the government line.