The Queen's copy of her keynote address omitted a vital paragraph commemorating the suffering of Polish Jews under Nazi occupation. A Buckingham Palace spokesman said "it was purely a mistake for which the Queen's advisers take full responsibility".
He added: "The reference was omitted entirely by mistake. The Queen had fully intended to read the sentence but it was missed out because of a typographical error - and it was not properly checked."
The Queen should have said: "Nor can we ever forget the suffering of the Polish people under Nazi occupation, nor the terrible fate of Polish Jews."
The slip is particularly unfortunate after recent controversy over the decision that the Queen should not visit Auschwitz during her historic state visit to Poland.
Instead, a ceremony at Warsaw's Umschlagplatz Jewish memorial was arranged at the last minute to commemorate the suffering of Polish Jews during the Second World War.
In a speech on Monday night, the Queen paid tribute to the courage and heroism of the people of Poland and Polish Jews, and it was intended that she should repeat the same sentiments yesterday. The speech to the Polish Parliament in Warsaw was, however, well received by Poland's political leaders who gave the Queen two standing ovations.
The Queen warned that Britain would not allow Russia to veto Poland's entry into the European Union and Nato. She said Britain was in sympathy with the Poles' desire to join, ". . . and we are determined that that aim cannot be subject to a veto by any other country". She added: "Poland needs Europe. But Europe also needs Poland."
Although she did not mention Russia by name, the Queen's strong warning, backed by the Foreign Office, is a clear reference to recent posturing by Boris Yeltsin's regime. The Queen said: "During the years of Europe's division, the idea that a British sovereign should address a freely-elected Polish Parliament would have seemed fantastic. But so much that seemed fantastic in those years has become reality."
Referring to Anglo-Polish co-operation during the War, she said: "As our two countries fought together against tyranny, I remember the Polish national anthem being played each week on the BBC along with those of our other gallant allies.
"And we will never forget, in my country, the courage of the Polish pilots, part of the `Few', to whom Churchill rightly said so much was owed. If Poland had not stood with us in those days, who knows - the candle of freedom might have been snuffed out?"
The war had joined Britain and Poland but later divided the two nations "for 1945 did not bring liberty to all", the Queen said. "The Poles who stayed in Britain founded a community which has given much to our national life. But their freedom was not reflected in their own country.
"So we rejoiced all the more so at Poland's recovery of full sovereignty and at your decision to seek membership of European and Western institutions.
"We strongly support the enlargement of the European Union and Nato, we are in sympathy with your aim to join these bodies, and we are determined that that aim cannot be subject to a veto by any other country."
The Queen received a standing ovation, part-way through her speech, when she quoted four words in Polish from a 1980s protest song, by Jan Pietrzak, against martial law in Poland - "Zeby Polska byla Polska" (May Poland be Poland). The packed chamber also rose from their seats at the end of the address.
Later the Queen and Duke of Edinburgh renewed their friendship with Poland's former president, Lech Walesa, who was their guest at Buckingham Palace and Windsor in 1991.