David Cameron is facing calls to press for the ending of EU trade concessions to Sri Lanka amid the continuing refusal of the government of President Mahinda Rajapaksa to co-operate with an international inquiry into human rights abuses.
The Commons Foreign Affairs Committee urged ministers to consider "all possible options" to persuade Sir Lanka to allow access to investigators from the United Nations Office of the High Commissioner for Human Rights (OHCHR).
Britain was instrumental in persuading the UN Human Rights Council to adopt the resolution passed last year which established the OHCHR inquiry into allegations of human rights abuses during Sri Lanka's long civil war.
It came after Mr Cameron used his visit to the Commonwealth Heads of Government Meeting held in Sri Lanka in 2012 to highlight continuing human rights concerns - including attacks on campaigners and journalists, violence against religious minorities and allegations of torture in police custody.
However, the response of the Sri Lankan government has been to threaten possible legal action against anyone testifying before the OHCHR inquiry while the parliament passed resolution not to allow the investigation team into the country.
In its report, the committee highlighted Sri Lanka's lucrative trade with the EU - worth 3.5 billion euros (£2.8 billion) - as an area where pressure could be brought to bear on the regime.
It said that despite the anti-Western rhetoric of President Rajapaksa, Sri Lanka - which has a 1.1 billion euro (£870 million) trade surplus with the EU - continued to benefit from favourable trade concessions from the EU.
The committee chairman, Sir Richard Ottaway MP, said: "Our Government must negotiate with EU partners to remove trade concessions from Sri Lanka if the government of Sri Lanka continues to deny the UN investigating team access into the country."
The committee also called on the Foreign Office (FCO) to explain what steps it had taken to monitor whether activists, refugees or journalists who spoke to Mr Cameron during his visit or a met British delegation which visited last year had suffered any reprisals.
In its report - covering all aspects of the FCO's human rights work - the committee also sharply criticised the Government's failure to meet a request from a UN special rapporteur on violence against women to visit the Yarl's Wood immigration detention centre, amid allegations staff were sexually exploiting vulnerable women detainees.
"We find it surprising that the Home Office was unable to facilitate a request, even at short notice, from a UN special rapporteur to visit Yarl's Wood," it said.
"It sets a dangerous precedent for other countries to follow suit and has caused embarrassment to the UK."
A spokesman for the FCO said it welcomed the Foreign Affairs Committee's acknowledgement of its work on promoting the right to freedom of religion or belief, assessing countries of concern, and the prevention of sexual violence in conflict.
He added: "The Prime Minister used his visit to Sri Lanka last year to highlight ongoing human rights issues in the country and the UK played a crucial role in securing a UN Human Rights Council resolution to establish its international investigation into alleged violations of international law on both sides of Sri Lanka's conflict.
"We continue to urge the Sri Lankan government to fully co-operate with this and to work with the international community in order to address the grievances of the past.
"The British High Commission in Colombo remains in contact with many of those who met the Prime Minister in Sri Lanka last year. As far as we are aware, no-one who met him or the delegation has experienced reprisals as a result."