Ministers from the UK and the EU's largest states have come under fire for holding meetings on issues about terrorism and immigration "in secret".
Peers expected the G6 meetings to attract widespread interest
The UK House of Lords EU Committee says the public has a right to know what goes on behind closed doors.
The peers claim important decisions are reached, yet no report is ever made to Parliament and no publicity is given about them by the Home Office.
However, the Home Office insists that meetings of the G6 are "transparent".
The last gathering of the G6 interior ministers was held in March, 2006.
Then Home Secretary Charles Clarke represented the UK at the meeting, which also included Germany, France, Italy, Spain and Poland - known as the G6, and who account for three quarters of the EU's population.
Ministers at the talks, which took place over two days at the Baltic resort of Heiligendamm, Germany, discussed their joint response to terrorism, illegal immigration and organised crime.
The peers said they would expect decisions taken at those meetings to "attract wide interest from the media", the European Parliament and national parliaments.
But they complained: "This was not the case.
"They discussed almost every aspect of EU policy of interest to them, and in many cases reached firm conclusions on the action which should be taken and the timetable for it.
"However, in the United Kingdom, the meetings went almost entirely unnoticed.
"The Home Office did not issue a press notice and the then Home Secretary Charles Clarke, who attended the meeting on behalf of the UK, did not make an oral or written statement to Parliament."
The peers added: "The Home Office seems on the contrary to have gone out of its way to disclose little or nothing about the meeting."
The meetings have been taking place since 2003, and the next, in October, is due to be chaired by new Home Secretary John Reid.
In their report, entitled "Behind Closed Doors", the peers said the only way they could get hold of any information about the latest talks was in an English translation from the German Ministry of the Interior.
"The committee believes that Parliament and the public have a right to know what is discussed and decided at these meetings," the peers said.
They say that they accept that particularly in an enlarged EU, it was "inevitable and desirable" for small groups of ministers to meet informally.
But they claim, the Heiligendamm meeting was one of a series of regular meetings between the G6 and "their influence on EU policy is decisive".
"They should not try to ride rough-shod over the 19 smaller member states," the peers said.
Lord Wright of Richmond, chairman of the committee, said ministers should not "ignore civil rights".
"They should not use these meetings to propose changes to previous policy decisions of the EU or the government," he said.
"Policy changes should be agreed through national parliaments and the community institutions - this will allow the smaller member states to have their say."
But a Home Office spokeswoman said the government welcomed the peers' report, adding that it would be providing a considered response "in due course".
"The G6 is transparent - they have a press conference at each meeting and the conclusions are published by the host nation," she said.
The spokeswoman said Home Office Minister Joan Ryan had "undertaken to ensure that the conclusions from the next meeting of the G6 this autumn will be published on the Home Office website".
She added that the G6 is an "informal grouping" of states that "do not have formal decision making powers".